From BitTorrent:

BitTorrent is a peer-to-peer (P2P) client designed to efficiently manage the downloading of large, high-quality, digital files such as video, music, and games. The client is used to search the Internet for legal torrent files, which can then be quickly downloaded to a user\'s machine. As files become more popular, the speed in which they can be downloaded increases through the use of a central tracker and peers. This technology saves time over traditional methods, while maintaining the integrity of the file. Version 4.4.1 may include unspecified updates, enhancements, and bug fixes.