Xen is a virtual machine monitor for x86 that supports execution of multiple guest operating systems in isolated environments.

Xen is a virtual machine monitor for x86 that supports execution of multiple guest operating systems with unprecedented levels of performance and resource isolation. Linux

A paravirtualisation engine for Linux, an efficient way to run multiple Linux OSes on one computer. Also runs BSD, Plan9 and other OSes. (See website for more information.)

Xen is a paravirtualizing virtual machine monitor, developed primarily by the Systems Research Group at the University of Cambridge Computer Laboratory.

Xen is a free virtual machine monitor for IA-32, x86-64, IA-64 and Power PC architectures. It is software that runs on a host operating system and allows one to run several guest operating systems on top of the host on the same computer hardware at the same time. Modified versions of Linux and Net BSD can be used as hosts.