A virtual private network (VPN) is an encrypted tunnel between two trusted end points.
When VPNs run between two locations or divisions of the same organization, the resulting connection is called an intranet. When VPNs run between an organization and trusted partner, the resulting connection is called an extranet. VPNs are also used on either an ad hoc or a long term basis to provision remote access for employees, suppliers, and customers.
VPNs can be provisioned over a variety of protocols. Some of these include: