Virtualization is the process of running a virtual instance of a computer system in a layer abstracted from the actual hardware.
It commonly refers to running multiple operating systems on a computer system simultaneously.
The applications running on top of the virtualized machine can appear as if they are on their dedicated device, where the operating system, libraries, and other programs are unique to the guest virtualized system and unconnected to the host operating system, which sits below it.
There are many reasons why people utilize virtualization in computing.
To desktop users, the most common use is to be able to run applications meant for a different operating system without having to switch computers or reboot into another system. For administrators of servers, virtualization also offers the ability to run other operating systems.
Still, perhaps, more importantly, it provides a way to segment an extensive system into many smaller parts, allowing the server to be used more efficiently by several different users or applications with additional needs. It also allows for isolation, keeping programs running inside a virtual machine safe from the processes taking place in another virtual machine on the same host.