VPN is the acronym for Virtual Private Network - a network type that uses a the Internet to provide remote networks or single machines with secure access to their organization's network avoiding expensive leased lines.
A VPN is a private network that uses a public network to connect remote sites or users. VPN use virtual connections routed through the Internet from the company's private network to the remote user or secondary site.
VPNs encapsulate data transfers using secure cryptographic methods and other security mechanisms to ensure that only authorized users can access the network and that the data cannot be intercepted.