A hypervisor is software that creates, runs, and monitors virtual machines (VMs). The physical hardware that a hypervisor is running on is referred to as a host. The hypervisor shares the host’s resources — such as CPU, memory and storage — among various guest VMs. A hypervisor provides the flexibility to run virtual machines that use operating systems different from the one run by the host machine. For example, a hypervisor running on a machine that uses Windows can create VMs that run Linux-based operating systems, and vice versa.

Hypervisors have been integral to the development of cloud computing. Consider virtual private servers, which are an example of individual VM instances that have been virtualized and optimized by a hypervisor on a larger host machine within a cloud provider’s data center.