Torrents (the small .torrent files) are hosted on servers or distributed via P2P. Each torrent is tracked by a tracker that your BitTorrent client connects to. The actual files that you download with the BT client come from other peers. Multiple ones at a time, that is. In a best-case scenario (and this isn't all that rare), you can download at several hundred KB per second... I got a 360KB/sec. download on a torrent once. Usually I get between 50-150KB/sec... which is very good I think.
