Virtualisation is the process of running a virtual instance of a computer system removed from the actual hardware. Most commonly, it refers to running multiple operating systems on a computer system simultaneously. To the applications running on top of the virtualised machine, it can appear as if they are on their own dedicated machine, where the operating system, libraries, and other programs are unique to the virtualised system and unconnected to the host operating system which sits below it.

A virtual computer system is known as a ‘virtual machine’ (VM): a tightly isolated software container with an operating system and application inside. Each self-contained VM is completely independent. Putting multiple VMs on a single computer enables several operating systems and applications to run on just one physical server, or ‘host’.

A thin layer of software called a “hypervisor” decouples the virtual machines from the host and dynamically allocates computing resources to each virtual machine as needed.