What is BitTorrent and How to Use It?
The most common methods of transferring files over the Internet are through a browser using "http" and through an ftp client. BitTorrent is a peer-to-peer application, where files are accessed directly from one computer to another, without the intervening use of an official server. Some examples of commercial peer-to-peer software are programs such as Kazaa and Gnutella.
With BitTorrent, files are broken into smaller fragments that can be re-assembled on the clients machine. The application finds the most efficent network connections to access the various pieces of the file, so it is very well suited to downloading large files such as music and videos.
The difference between BitTorrent and applications such as Kazaa, is that BitTorrent is open source. Recommended BitTorrent applications for PC: Download: Burst and Download: BitTornado. For Mac OSX: Download: Official Client Version 3.1
According to the BitTorrent FAQ and Guide, BitTorrent is a useful program for accessing newer, high demand large files such as video downloads and music downloads, as BitTorrent, unlike other file transfer protocols, becomes more efficient as the number of people interested in a certain file increases.
See the Wikipedia entry about BitTorrent for more information.