A VPN is a virtual network, built on top of existing physical networks, that can provide a secure communications mechanism for data and other information transmitted between networks. Because a VPN can be used over existing networks, such as the Internet, it can facilitate the secure transfer of sensitive data across public networks. This is often less expensive than alternatives such as dedicated private telecommunications lines between organizations or branch offices.
VPNs can also provide flexible solutions, such as securing communications between remote telecommuters and the organization’s servers, regardless of where the telecommuters are located. A VPN can even be established within a single network to protect particularly sensitive communications from other parties on the same network

