BitTorrent is a popular file sharing program. It is most commonly used for large file downloads, such as movies and operating systems.

BitTorrent is also one of the most dangerous file sharing programs out there. With any download, you will recieve a small text file with the words "tracked by (webpage, eg: demonoid.com)". That webpage keeps a list of users IP addresses so other users can connect to them. This list of IPs is easily easily accessible to orginazations like the MPAA or the RIAA. In fact, nearly everyone who downloaded the partial source code for Microsofts' Windows platform recieved a letter from Microsoft.

A program that creates a network between users to make your downloads go really fast and all but eliminates leeching. It's pretty cool, dudes.

the best way to get a fuckload of viruses

A media grabber used to torrent media, as simple as that,