Online Computer Dictionary

A popular, distributed form of peer-to-peer file sharing that enables a client program to fetch different parts of a file (a "torrent") from different sources in parallel. The system is designed to encourage users to make downloaded data available for others to upload. This is aided by a scheme for exchanging unique identifiers, commonly stored in ".torrent" files. A downloader who does not serve data to others is called a "leech". A "seed" is a computer that has a complete copy of a file, possibly the original.

The bittorrent.com site claims there are over 100 million users as of 2007-03-24.

Most of the data is copyright material like films or commercial software.

http://www.bittorrent.com/what-is-bittorrent.