Concept of VPN

A Virtual Private Network is a safe communication method between two points through a public network. You can find a detailed definition of VPN on:

http://ibvpn.com/blog/2010/02/what-is-a-vpn-service/

You will also find there instructions on how to configure a VPN and much more VPN is Virtual Private Network. It is used as a means to extend private network across public network. An example for VPN is internet.