What is TOR (The Onion Router)?

TOR (The Onion Router) is the largest and most popular implementation of onion routing that is used on the dark web. Onion routing is a method of transmitting data over a network by securing and anonymizing it using multiple separate layers of encryption. The encryption is applied using different keys at different locations on the journey over the network and then unpacked at the destination – like taking the layers off an onion.

See Onionland and Onion Routing.