A hypervisor is a piece of software, firmware or hardware that creates and runs virtual machines.
There are two types of hypervisors: type 1 and type 2.
Type 1 hypervisors are also called bare-metal hypervisors. They run on top of the host machines’ hardware, controlling CPU scheduling and memory allocation, as well as emulating storage and networking devices’ capabilities. Any guest OS can run on these virtual machines as if they were real bare-metal computers.
Type 2 hypervisors run on a host operating system, the same way as any other application running on the OS. They abstract guest operating systems from the host OS.
Virtualisation reduces hardware costs by running multiple workloads on the same physical machine. Guest OSes can be moved between hosts quickly in the event of host machine failure or maintenance. Creating and configuring a guest machine is usually faster and simpler than configuring it on bare-metal hardware.