A virtual private network (VPN)

Any arrangement that provides connections between offices, remote workers, and the Internet without requiring dedicated lines, also referred to as private networks between sites. The term "virtual" refers to the fact that these VPNs provide the features of private lines; they are virtually private.

An alternate definition: A VPN is a communications network tunneled through another network, and dedicated for a specific network. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features.