Linux-VServer is a virtual private server implementation done by adding operating system-level virtualization capabilities to the Linux kernel. It is developed and distributed as open source software under GNU GPL.
Linux-VServer is a jail mechanism in that it can be used to securely partition resources on a computer system (such as the file system, CPU time, network addresses and memory) in such a way that processes cannot mount a denial-of-service attack on anything outside their partition. This is sometimes referred to as a "jail" approach, because it closely resembles a feature called "jails" that is pretty well-known for the FreeBSD operating system. FreeBSD jails are, in turn, an extension of the chroot jail concept, which has long been supported by many UNIX kernels, including the Linux kernel.
Linux-VServer offers a simple way to run several virtual servers on one piece of physical hardware. While it lacks some of the flexibility of more complex virtualization schemes, it is simple to implement and is capable of excellent performance.
Linux-VServer, and similar software like OpenVZ, take a "lightweight" approach to virtualization, essentially segmenting a single Linux kernel environment into virtual machines with separate file systems, process tables, and network addresses.
Read more at Linux.com: Installing Linux-VServer