"A hypervisor is a software technology used in virtualization,
which allows several operating systems to run side-by-side on a
given piece of hardware.
"Unlike conventional virtual-computing programs, a hypervisor
runs directly on the target hardware's "bare metal," instead of as
a program in another operating system. This allows both the guest
OSes and the hypervisor to perform that much more efficiently.
• VMware ESX / vmkernel
• Microsoft Hyper-V
• Logical Domains / Oracle VM
• Wind River Hypervisor