TOR stands for The Onion Router. Tor is an system set up to anonymize web traffic, protecting a user mainly from malware and other issues. It is used by a wide range of organizations and people that want to improve their safety and security on the Internet. Tor can anonymize things that use the TCP protocol like web browsing and publishing, instant messaging, IRC, SSH etc.
Tor's main goal is to stop "traffic analysis". This is a network monitoring system that threatens personal anonymity and privacy, confidential business activities and relationships, and state security. Tor works by bouncing communications around a network of servers called "onions" between the source and the destination.
The Electronic Frontier Foundation supports the TOR network. A branch of the U.S. Navy uses Tor for open source intelligence gathering, and one of its teams used Tor while deployed in the Middle East recently. Law enforcement uses Tor for visiting or surveilling web sites without leaving government IP addresses in their web logs, and for security during sting operations.
Misuse
When you get a service that anonymize Internet communications, what you will inevitably get with it is misuse of the service. Tor was being widely used by BitTorrent users to keep themselves anonymous incase any anti-piracy organizations were monitoring people sharing pirated content. The people who work on TOR really discourage its use since BitTorrent and other P2P systems use up way too much bandwidth and destabilize the TOR network.
