A hypervisor is a program that allows multiple operating systems to share a single hardware host. In KVM, the Linux kernel acts as a Type 2 Hypervisor, streamlining management and improving performance in virtualized environments. The hypervisor creates virtual machine (VM) environments and coordinates calls for processor, memory, hard disk, network, and other resources through the host OS. KVM requires a processor with hardware virtualization extensions to connect to the guest OSs.
KVM has been bundled along with the Linux operating system (OS) since 2007 and can be installed along with the Linux kernel. Numerous guest OSs can work with KVM including BSD (Berkeley Software Distribution), Solaris, Windows, Haiku, ReactOS, Plan 9, and the AROS Research OS. In addition, a modified version of QEMU ("Quick Emulator") can use KVM to run Mac OS X.