What is a virtual machine (VM)?

An intro to virtualization and the benefits of VMs

Virtual machines: virtual computers within computers

A virtual machine, commonly shortened to just VM, is no different than any other physical computer like a laptop, smart phone, or server. It has a CPU, memory, disks to store your files, and can connect to the internet if needed. While the parts that make up your computer (called hardware) are physical and tangible, VMs are often thought of as virtual computers or software-defined computers within physical servers, existing only as code.

An illustration of virtual computers stored inside physical computers as code.

How does a virtual machine work?

Virtualization is the process of creating a software-based, or "virtual" version of a computer, with dedicated amounts of CPU, memory, and storage that are "borrowed" from a physical host computer—such as your personal computer— and/or a remote server—such as a server in a cloud provider's datacenter. A virtual machine is a computer file, typically called an image, that behaves like an actual computer. It can run in a window as a separate computing environment, often to run a different operating system—or even to function as the user's entire computer experience—as is common on many people's work computers. The virtual machine is partitioned from the rest of the system, meaning that the software inside a VM can't interfere with the host computer's primary operating system.

What are VMs used for?

Here are a few ways virtual machines are used:

Building and deploying apps to the cloud.
Trying out a new operating system (OS), including beta releases.
Spinning up a new environment to make it simpler and quicker for developers to run dev-test scenarios.
Backing up your existing OS.
Accessing virus-infected data or running an old application by installing an older OS.
Running software or apps on operating systems that they weren't originally intended for.

What are the benefits of using VMs?

While virtual machines run like individual computers with individual operating systems and applications, they have the advantage of remaining completely independent of one another and the physical host machine. A piece of software called a hypervisor, or virtual machine manager, lets you run different operating systems on different virtual machines at the same time. This makes it possible to run Linux VMs, for example, on a Windows OS, or to run an earlier version of Windows on more current Windows OS.

And, because VMs are independent of each other, they're also extremely portable. You can move a VM on a hypervisor to another hypervisor on a completely different machine almost instantaneously.

Because of their flexibility and portability, virtual machines provide many benefits, such as:

Cost savings—running multiple virtual environments from one piece of infrastructure means that you can drastically reduce your physical infrastructure footprint. This boosts your bottom line—decreasing the need to maintain nearly as many servers and saving on maintenance costs and electricity.
Agility and speed—Spinning up a VM is relatively easy and quick and is much simpler than provisioning an entire new environment for your developers. Virtualization makes the process of running dev-test scenarios a lot quicker.
Lowered downtime—VMs are so portable and easy to move from one hypervisor to another on a different machine—this means that they are a great solution for backup, in the event the host goes down unexpectedly.
Scalability—VMs allow you to more easily scale your apps by adding more physical or virtual servers to distribute the workload across multiple VMs. As a result you can increase the availability and performance of your apps.
Security benefits— Because virtual machines run in multiple operating systems, using a guest operating system on a VM allows you to run apps of questionable security and protects your host operating system. VMs also allow for better security forensics, and are often used to safely study computer viruses, isolating the viruses to avoid risking their host computer.

Frequently asked questions

The process of creating a software-based, or "virtual" version of something—whether that be compute, storage, networking, servers, or apps—is called virtualization. Virtualization as a technology enjoys a lengthy history, and today, it's still very relevant to building a cloud computing strategy. So, virtualization is the process, and the machines made using that process are most commonly called virtual machines or just VMs.
Multiple virtual machines can run simultaneously on the same physical computer, all managed by a hypervisor. A hypervisor is the software that integrates the physical hardware and the VM's virtual "hardware". This is very similar to how an operating system in a typical computer works: much like a school crossing guard helps multiple students move safely back and forth across a busy intersection, the hypervisor makes sure each VM gets the resources it needs from the physical server in an orderly and timely manner.
This is the foundational category of cloud computing services. With IaaS, you rent IT infrastructure—servers and virtual machines (VMs), storage, networks, and operating systems—on a pay-as-you-go basis from a cloud provider such as Microsoft Azure.

Learn more about IaaS
Yes, and no! Azure Virtual Machines is the Azure infrastructure as a service (IaaS) used to deploy persistent VMs with nearly any VM server workload that you want. They are image service instances that provide on-demand and scalable computing resources with usage-based pricing.

So, Azure Virtual Machines is the service that provides VMs optimized for general purpose or storage, memory, compute, and graphics-intensive workloads and are offered in a variety of types and sizes to meet your needs and keep your budget in check.

Learn more about Azure IaaS
Spot VMs are part of services offered by a cloud provider, such as Microsoft Azure, that provides scalable compute capacity at deep discounts.

Spot VMs are ideal for workloads that can be interrupted, such as:
- Select high-performance computing scenarios, batch processing jobs, or visual rendering applications.
- Dev/test environments, including continuous integration and continuous delivery workloads.
- Big data, analytics, container-based, large-scale stateless applications.
Learn more about Azure Spot Virtual Machines
Azure Disk Storage is a service offering high-performing, highly durable block storage designed to be used with Azure Virtual Machines. With unmatched resiliency, seamless scalability, and built-in security, Azure Disk Storage delivers the price-performance you need for your mission and business-critical apps.

Learn more about Azure Disk Storage
In general, hybrid cloud computing refers to a cloud environment that combines public cloud and on-premises infrastructure, including private cloud, by allowing data and apps to be shared between them. It expands your cloud deployment options, offering greater flexibility to scale resources and take advantage of cloud tech innovations, while giving interoperability with on-prem environments.

Get an intro to public, private, and hybrid clouds
Cloud services providers sometimes call cloud computing services a "stack", because they build on top of one another. While infrastructure as a service (IaaS) represents the foundational element in the stack, other services are often used together with IaaS, such as platform as a service (PaaS), software as a service (SaaS), and serverless computing.

Learn more common cloud computing terms