Virtual Machines Explained: What They Are, How They Work, and Why They Matter

A virtual machine (VM) is a software-based computer that runs inside your existing computer. It has its own operating system, apps, and virtual hardware, so you can experiment, test, or run different operating systems without changing your main setup.

Whether you're on a Mac and need a Windows-only business app, or you're a developer who wants clean, repeatable environments for testing, a virtual machine lets you spin up exactly what you need on one physical machine. In this guide, we'll explain how VMs work, when they're the right tool, and what to consider when you choose your setup.

With Parallels Desktop for Mac, you can run Windows side by side with macOS in a virtual machine that feels like a native part of your Mac – no reboot required.

Key takeaways

• A virtual machine is a software-defined computer that runs as a guest operating system on a physical host. You assign computing resources such as CPU, memory, storage, and network, and use it much like a separate PC. On a single host machine, you can run multiple virtual machines side by side without rebooting.
• Common reasons to use VMs include running Windows apps on a Mac, creating reproducible development and testing environments, and improving security and recovery with isolation and snapshots. VMs provide strong separation between workloads while still sharing the underlying hardware.
• On a Mac, Parallels Desktop lets you run Windows and other operating systems alongside macOS with deep integration features like shared clipboard, files, and devices. It’s a mature virtualization platform that’s been evolving since 2006 and is officially recognized by Microsoft as an authorized solution for running Windows 11 on Mac computers with Apple silicon. You can download a free trial from the official Parallels website to see how a VM fits your workflow.

How virtual machines work, under the hood

Before you pick a virtualization tool, it helps to understand how one physical machine can safely act like many. At the center is the hypervisor, also called a virtual machine monitor (VMM). It sits between each virtual machine and the underlying hardware, scheduling CPU and memory and coordinating access to devices so that VMs cannot interfere with each other or the host.

Storage and networking are often handled by separate parts of the virtualization stack. They expose virtual disks and virtual network interfaces to each VM, while the hypervisor and I/O stack translate those requests into real reads, writes, and packets on the physical host. In everyday language, people often use “hypervisor” to refer to this whole stack, not just the low-level scheduling component.

The hypervisor

A hypervisor multiplexes hardware resources between multiple virtual machines running on the same physical host. In most environments you will see two broad categories, and the differences explain where each one makes sense.

Type 1 (bare-metal) hypervisors run directly on the physical server hardware. They are purpose-built for virtualization and are commonly used in data centers, cloud Infrastructure as a Service (IaaS), VDI platforms, and other high-performance or security-sensitive workloads. Because they sit directly on the hardware, they typically offer:

• High VM density and strong performance
• Strong isolation and security controls
• Centralized, enterprise-grade management tools

The trade-offs are that they can be more complex to deploy and manage, often require compatible hardware, and usually do not provide the everyday desktop experience of a full client OS.

Type 2 (hosted) hypervisors run as applications on top of a host operating system such as Windows, macOS, or Linux. They are widely used for developer and test environments, running Windows on a Mac, demos, and short-lived sandboxes.

Hosted hypervisors tend to be the easiest way to get started with virtual machines on a laptop or desktop. They offer tight integration with the host—shared clipboard and files, drag-and-drop, and broad device support—making a VM feel like another app window. In return, there is extra overhead compared to bare-metal hypervisors, peak performance is lower, and isolation is influenced by the security posture of the underlying host OS.

Modern processors include hardware-assisted virtualization features that help the hypervisor map memory and device calls efficiently. Combined with today’s more capable CPUs, RAM, and storage, this lets you run several virtual machines alongside your usual browser tabs and productivity apps without bringing a physical computer to a halt.

Types of virtual machines you will see

This topic goes beyond the single VM on your laptop. Virtual machine technology spans everything from your local physical computer to hyperscale cloud regions, and it even appears inside language runtimes.

System VMs

System virtual machines are what most people mean when they say “a VM.” They run a full operating system image—such as Windows, Linux, or (in supported scenarios) macOS—as a guest operating system on top of a physical host.

These VMs:

• Power server virtualization in the cloud and in on-premises data centers
• Run desktop and training labs without needing a separate physical machine for every user
• Let teams validate changes against realistic clones of production environments
• Close “app gaps,” for example, by running Windows apps on a Mac in a desktop virtual machine

When you run Windows or Linux on a Mac using Parallels Desktop, you are using a system VM: a complete OS with its own apps, settings, and virtual hardware that lives alongside macOS.

Process VMs

Process virtual machines operate at the application level rather than emulating an entire PC. A Java virtual machine (JVM) or the .NET Common Language Runtime (CLR) runs bytecode on many platforms, providing portability across different operating systems without compiling native binaries for each physical server type.

Instead of virtualizing a full computer with its own kernel, a process VM emulates an execution environment for one application or runtime. This is why the same Java or .NET application can run on different operating systems, while still sharing the underlying hardware and host OS kernel.

VM versus container

VMs and containers both isolate workloads, but they draw the line at different layers. A VM virtualizes hardware, containers package processes that share the host kernel. The choice affects isolation, boot time, density, and cross OS compatibility.

Three quick comparisons:

Use this guide: if you need strong isolation, mixed OS support, or Windows utilities alongside macOS, choose a VM. If you need to scale microservices quickly, run many stateless replicas, and keep images small, containers are a better fit.

They are native to Linux. On Windows PCs and Macs, container platforms start a lightweight virtual machine to run Linux behind the scenes, and your containers operate inside that VM.

Common VM use cases

Virtual machines per host unlock a long list of practical scenarios.

Each one trades a small amount of overhead for big gains in flexibility:

• Run Windows apps on a Mac, including legacy tools tied to a specific OS release, using a desktop virtual machine with file and clipboard integration.
• Create development and testing environments that mirror production, with snapshots for fast rollback and scripted provisioning so that bugs can be reproduced reliably. Teams that ship frequently prefer to develop on a virtual machine to maintain reproducible environments across laptops and CI.
• Education and training labs that allow learners to try out risky changes safely, then reset in one click.
• Regulated or high-trust isolation, where policy requires a separate virtualized environment for each tenant.
• VDI and DaaS platforms that centralize desktops while keeping per-user isolation.
• Disaster recovery with image-based backups and point-in-time restore, turning a bad patch into a quick revert rather than hours of rebuild.

These scenarios primarily involve servers and clouds. VMs are the backbone of the internet and are widely used on servers. When teams compare them to dedicated servers, they often choose VMs because capacity planning is simpler and the path from laptop to cloud is clear.

Virtual machines in the cloud

Infrastructure as a Service runs on VM instances. Images, such as a golden Windows or Linux template, allow predictable scale-out across regions. You still choose vCPU and memory sizes, attach storage, and put instances behind a network interface.

Many teams prefer VMs over containers or serverless when they need deep OS control, specific kernel modules, or to lift and shift on-premises workloads without refactoring.

Choosing your guest OS

Picking the right guest OS ensures predictable performance and licensing sanity, especially when running multiple virtual machines side by side on the same host.

Windows in a VM

Windows 10 has reached the end of support, and although extended options are available, they are temporary. The recommended path is Windows 11, which provides current security baselines and driver support. If your goal is to run Windows on a Mac, start with the Getting Started guidance and confirm app compatibility for Intel-based apps on Windows 11 for Arm.

Linux in a VM

Linux distributions like Ubuntu LTS, Fedora Workstation, and Debian are popular among developers due to their package availability and lighter resource profiles. They shine for CI runners, local Kubernetes labs, and headless services in testing environments that do not need a heavy desktop.

macOS in a VM

On Apple silicon, macOS virtualization has specific constraints around licensing and feature support. Review the supported scenarios and compliance language before planning a macOS guest OS, especially for on-premises labs where policy is a key consideration.

Performance and sizing basics

Before dialing in CPU and memory, remember how allocation works in a VM. You assign a maximum amount of your Mac’s resources to the VM; those resources aren’t permanently “locked away.”

With Parallels Desktop on macOS, the host OS still balances CPU and memory across active processes. However, if you allocate too much to the VM, you can starve macOS and your Mac apps, causing sluggishness in both the host and the VM. Don’t allocate everything.

Parallels helps here: choose Automatic allocation (set by the selected profile, such as productivity, with Office apps by default), and it will size the VM in line with your hardware. You can fine-tune later if needed.

Starter sizing guidelines:

• Office productivity: 2 vCPU, 4–8 GB RAM
• Developer workloads (compilers, Docker inside the VM): 4 vCPU, 8–16 GB RAM

Use these as ceilings to begin with, keep some headroom for macOS, and adjust upward only if you see consistent bottlenecks inside the VM.

You don't need a giant physical server to achieve good results, but a few guardrails can help. For office productivity, start at 2 vCPU and 4 to 8 GB of RAM. For developer work with IDEs and Docker inside the VM, plan 4 vCPU and 8 to 16 GB of RAM.

For light 3D or UI-intensive work, 3D acceleration is already enabled by default in Parallels Desktop. Start with 4–6 vCPU and around 16 GB RAM as an upper bound, only if Automatic doesn’t feel smooth.

In general, stick with Automatic allocation, which sizes resources for your hardware. If you’re not happy with the performance, make measured, experimental changes: bump memory or vCPU by a step, test, and either revert or keep the change based on the results.

You don’t need to manage drivers. Parallels Tools installs the optimized paravirtualized drivers automatically, and Parallels’ Windows images include them out of the box, so nothing to configure or “use.” They update with Tools as needed.

Keep in mind that oversubscription has limits; the hypervisor can juggle busy VMs for a while, but the underlying hardware still sets the ceiling. Parallels Desktop uses expanding disks, so you don’t need to pre-allocate a huge virtual drive; space on your Mac is only consumed as files are added in the guest OS.

Just keep enough free space on the Mac for OS updates and snapshots, and periodically delete old snapshots to reclaim storage.

Security and isolation basics

Snapshots provide rapid rollback from a bad change. Network isolation, such as host-only or NAT modes, reduces exposure while still allowing updates.

Features like shared clipboard and shared folders are convenient, and they also bridge trust boundaries, so disable them for higher-risk work. Finally, host hygiene still matters. A VM is only as safe as the physical host that runs it.

Getting started on a Mac with Parallels

Getting your first VM running on a Mac takes just minutes, and the setup choices you make now significantly impact performance, security, and day-to-day convenience. Follow this streamlined walkthrough to install Parallels Desktop, select the right image, and configure resources and integrations so that Windows or Linux feels at home alongside macOS.

Use it as a checklist the first time, then save your tuned template for future projects:

1. Install Parallels Desktop, then open it from the Applications folder.
2. Use the wizard to create a virtual machine from an image or install media.
3. Select an image, such as Windows 11, Linux, or macOS, where supported, and confirm the licensing.
4. Allocate resources based on the sizing guidance above and your physical machine.
5. Install Parallels Tools for better integration and performance.
6. Optimize settings, including Coherence, sharing, and security preferences, before launching for the first time.

To optimize the performance of a virtual machine on Apple silicon, test it with your daily tools first and verify the GPU and USB passthrough settings for your devices.

What runs best in a Windows 11 VM on Apple silicon, and where it still struggles

On M-series Macs, Windows 11 on Arm delivers excellent responsiveness for many developer and knowledge work tasks. Workloads that are compute-bound but not GPU-bound, such as compilers, test runners, and command-line tools, run well when you provide the VM with adequate vCPUs and RAM.

Recent optimizations for the Windows 11 24H2 release enhance the emulation of Intel-based apps, and certain computational tasks can experience up to an 80 percent performance boost due to improvements in the Prism emulator within Windows 11 on Arm. That means many productivity and development tools feel native enough to trust for daily use.

You will still encounter friction with apps that rely on specific kernel drivers, outdated 32-bit plug-ins, or specialized GPU features. Some games and pro 3D tools rely on vendor-specific paths that do not translate cleanly to a virtualized environment today. Treat these as outliers to validate early rather than surprises late.

A three-question litmus test, VM or containers for day-to-day dev and test

Use this quick decision rule to avoid months of second-guessing:

• Do I need to replicate an entire operating system, or just the application’s environment?
• Is consistency and portability across local, staging, and production my top priority?
• Do I require robust, hardware-level isolation for security-sensitive workloads?

If you answered “entire OS,” “yes,” or “require,” a VM is likely the safer default. If your services already run in containers and you only need the app layer, containers inside a lightweight Linux VM can strike a practical balance.

Minimum viable hardening for a Parallels Desktop VM on a developer Mac

Security does not have to slow you down.

Apply this compact checklist to balance convenience and risk, then tune as your projects mature:

• Start with a clean, patched image and disable auto login in the guest.
• Use separate standard accounts for daily work and reserve admin accounts for installations.
• Turn off shared clipboard and shared folders for sensitive projects, re-enable only when needed.
• Prefer NAT networking, and restrict inbound ports to known services.
• Enable disk encryption in the guest OS if it contains sensitive data or secrets.
• Keep snapshots brief, for example, during risky changes, then delete them after verification.
• Treat each VM as a project boundary, keep work and personal separate by design.

This baseline adds minutes to setup, and it reduces the likelihood that a compromise can jump between environments.

Match the hypervisor to your goal

Virtual machines give you a clean, flexible way to run different operating systems on your laptop or in the cloud, all without messing up your main setup. Pick a Type 1 or Type 2 hypervisor based on what you care about most (raw performance and scale, or tighter host integration), then size each VM to the workloads you actually run. Ready to spin one up and see how it fits your flow?

Start a free trial today to run a desktop virtual machine on your Mac in minutes.

Troubleshooting and FAQs

Here are the quick fixes and sanity checks we reach for most often. This short FAQ addresses the real-world challenges that arise when running Windows 11 VMs on Apple silicon, including sizing questions, graphics quirks, and Intel app compatibility issues. Skim it now, then keep it handy the next time a setting or workflow behaves differently than you expect.

How much RAM and CPU should I allocate?

Start with 2 vCPU and 8 GB for general office use, 4 vCPU and 16 GB for active development, then measure and adjust after a full day’s work.

Will older apps that target Intel run in Windows 11 on Arm?

Many do, and recent improvements in the Prism emulator raised compatibility and performance, but validate apps with special drivers early.

How does 3D acceleration affect performance?

Enable it for UI heavy apps and light 3D, and check your VM’s GPU settings if you see rendering or frame rate issues.

Is a VM the same as an emulator?

A VM virtualizes hardware to run full operating systems. Emulators translate instruction sets. Some scenarios combine both, for example, Intel app emulation inside a Windows 11 on Arm guest.

How do I keep work and personal separate on one Mac?

Create isolated VMs with separate accounts and disable sharing between them by default, then move files through controlled channels.

Ready to Try It?

Whether you’re trying to play PC games on a Mac, keep your dev environment tidy, or give your IT team more flexibility, Parallels has a solution:

Download your free trial of Parallels Desktop and start running VMs on your Mac today.