A computer inside another computer. Whoa.

“Virtualization is the abstraction of IT resources that masks the physical nature and boundaries of those resources from users,” according to Gartner.

As trippy as that definition sounds, the truth is much simpler. Virtualization software allows you to run two or more operating systems using only one PC. So it’s like two (or more) computers in one. One is physical, and the others are virtual. More broadly, virtualization can refer to any instance of one IT resource hosting multiple other IT resources, including applications, servers, clients, storage capacities, or networks.

Virtualization software, also called a hypervisor, is what allows one computer or server to host multiple operating systems.

What does virtualization software do?

Your resources are finite. Virtualization enables you to get more value out of them. With it, you can run more software and complete more processes with the same amount of hardware.

Back it on up

Virtualization makes backing up your entire operating system or server installation as easy as backing up a group of files. That’s because your virtual OS is just a series of files.

Let’s say a hacker takes down your mail server. If you’ve been running it on a virtual machine, you can just restore the old version.

Run a different OS

Let’s say you use Windows every day, but are dying to try Linux. Or, you’ve got an application that only works for Mac OS. Sure, you could repartition your computer’s hard drive. But the first step to doing that should be taking a snapshot of your computer. AKA, what virtualization does. Then you have to worry about whether the computer will let you shrink it enough.

Having a desktop version of Linux for occasional use obviates the need to install PuTTY on Windows. Linux has tools to communicate via secure shell (SSH) built-in. And if your mail or Web services are Linux-based, virtualization will make communicating with the server easier.

Run ancient apps

Other nifty things virtualization enables include running apps on old operating systems. Let’s say you’ve got a program that only runs on Windows 8, but you upgraded to Windows 10. No problem, just use virtualization to run Windows 8 on the same computer.

Look at dirty files

Virtualization software also allows you to create a snapshot of your computer. What this means is that it saves all the settings and hard drive contents away in another part of the computer. So you can make changes to a small part of the computer without making changes to the rest. And, more importantly, it means you can easily reverse those changes by reverting back to the earlier state.

So let’s say you get a file that you really need to read or watch or listen to, but it’s infected with a virus. If you take a snapshot of your machine before opening the file, you can view/watch/listen to the file and then revert back to your saved version.

Protect your computer from browser stank

Hackers have successfully exploited all four of most popular browsers — Chrome, Internet Explorer, Firefox, and Safari.

Keep your computer safe from browser hacks by running your browser of choice in a sandbox.

From Tor to Firefox, even if your browser or plugin gets hacked, your computer can stay safe with virtualization. Same as the corrupted file, a snapshot restores everything to normal even if a hack occurs.

Try an application on for size

Want to see how a new program or application will interact with your other applications without having to uninstall and reinstall every application if they can’t play nice? If you create a copy of an existing installation of an operating system and its data, you can run a virtualized instance and make sure configuration changes or updates won’t mess anything up without putting your actual installation and data at risk.

Other benefits

“Virtualization can also improve disaster recovery, load balancing, and software testing; reduce hardware costs; save energy; and reduce the physical size of your company’s data center,” writes David Coursey for PCWorld.

The ultimate point of virtualization software is flexibility.

Virtualization software enables IaaS, or Infrastructure as a Service. In this model, a company hosts customers’ hardware, software, servers, storage, and other infrastructure components. Users pay for for what they use in an hour, week, or month. IaaS makes resources highly scalable according to demand, which is great for temporary or experimental workloads and workloads that can change unexpectedly.

Virtualization Software Options

The 800-lb gorilla is VMwarewrites Kenneth Hess for ServerWatch. “VMware dominates the server virtualization market. Its domination doesn’t stop with its commercial product, VMware vSphere. VMware also dominates the desktop-level virtualization market and perhaps even the free server virtualization market with its VMware Server product. VMware remains in the dominant spot due to its innovations, strategic partnerships and rock-solid products.” Check out VMware’s free hypervisor.

Next to VMware in terms of popularity is Hyper-V, the only non-Linux server virtualization software option to really compete with VMware. “Not easily outdone in the data center space, Microsoft offers attractive licensing for its Hyper-V product and the operating systems that live on it,” according to Hess. With each new Windows Server release, Hyper-V has gotten closer to VMware for all-Microsoft shops, especially those “enterprises looking to leverage the company’s Azure cloud services as well as those interested in managing both on-premises Hyper-V services and Azure services.” Features including live migration and failover clustering make it an attractive option.

Applications Manager by ManageEngine is another option in the space.

ManageEngine Applications Manager is more than a hypervisor. It also offers application and data center monitoring. Use it to ensure your web applications, web servers, application servers, databases, and systems are up and up-to-date.

According to Heroix, “The cost difference for hypervisors is primarily based on licensing advanced features – so to determine your licensing costs, you need to determine which advanced features are required in your environment.”

To learn more about your options, check out Wikipedia’s comparison of platform virtualization software. It was updated this month, but, fair warning, that doesn’t mean everything in it is up-to-date. Wikipedia’s comparison of application virtualization software was updated last month.

You can also read reviews of virtualization software at Capterra.

Any important aspects of virtualization software that I missed? Let me know in the comments!