tunnel - Definition from the Hotspot Shield Glossary

A tunnel involves creating a path between two points on a network using encapsulation of data packets.

In conventional terms a tunnel creates a path (traditionally underground) between two points of entry to bypass other methods of getting between the two points i.e. over ground. A tunnel in networking uses the same principal, but the two points are two devices connected on a public network, and a private connection will be created (the tunnel) where the information can be securely transmitted using encryption and encapsulation. A tunnel is an important part of PPTP and L2TP protocols which are both types of tunneling protocol used to transfer and access secure data.