Torrents (BitTorrent)
Torrents are files available for download spread across the net on the computers of people just like yourself. When you download a torrent, you download bits from anyone who has made the file available via their torrent client. This means that because you are not downloading all the file from one source, the bandwidth for the hosts is greatly reduced.
It can also mean that the file is more difficult to complete while you wait for various hosts to turn on their machine. Once you begin downloading the parts that you download are made available to everyone else. It is considered polite to continue making the file available for download for at least a day or two after your download is complete.
http://en.wikipedia.org/wiki/BitTorrent
Azureus
http://azureus.sourceforge.net/download.php
