BitTorrent is a peer-to-peer program developed by Bram Cohen and BitTorrent, Inc. used for uploading and downloading files under the BitTorrent protocol. In the protocol, a "Tracker" hosts information about .torrent files (but not the actual files themselves). Using the .torrent files, BitTorrent users can "Leech" (download) the files. Once a "Leecher" gets 100% of the file(s) he become a "Seeder" and helps "Seed" (upload) the files to other Leechers.
BitTorrent was the first client written for the protocol. Before version 6.0, BitTorrent was written in Python, and was free software. The source code for versions up to and including 3.4.2 were distributed under the MIT license and versions 4.x and 5.x were released under the BitTorrent Open Source License, a modified version of the Jabber Open Source License. Since version 6.0, BitTorrent is a rebranded version of µTorrent. As a result, its source is closed.
The BitTorrent protocol now has many clients, for example :