It's a file sharing program essentially. You use it to download that stuff, and so long as you leave the download open (even after completion)... others can grab that file from you. But it doesn't just grab from a singular source... it grabs from all people who have their bit torrents open.
Try this and grab the B++ version..
http://bittorrent.com/
And then check out
http://www.suprnova.org
Once installed the bit torrent recognizes .torrent file extensions in IE... if you click on a movie or tv show or what have you... it'll automatically launch the bit torrent download program.