VPN - Virtual Private Network
A Virtual Private Network is a kind of network that is similar to a private network, but established using the public network, we call 'Internet'. VPN allows a user or an organization, send or receive data across a public network with the functionalities and security features of the private network.
VPN systems use authentication and encryption techniques to ensure that only the authorized user can access the company's network, data or physical resources. VPN technology is quite useful for those organizations, government institutions or educational institutions who can't afford to have a large private network, or creating a private network is not feasible for them.
In order to gain access to a Virtual Private Network, a user must authenticate himself to the secure server. A user, typically a VPN client installed on a remote user's computer, authenticate itself to gain access to the organization's resources. This authentication and added encryption feature makes VPN - a highly secure network over a less secure public network.