Torrent is a software wich allows the user to d/load a file known as a torrent file (wich itself is not a COMPLETE FILE, in itself)
Its just a medium by wich u can connect ot ppl on the net using a Bit Torrent s/ware liike uTORRENT or Azureus and then run that torrent file (mainly in kb size) to connect ot other ppl having SOME parts of the file (known as incomplete users or in TORRENT terms as LEECHERS) and ppl who hv the COMPLETE parts of the same file (known as complete users or in TORRENT Terms as SEEDERS)
NOTE: IN NOW way TORRENTS are associated with ILLEGAL DOWNLOADS (Always). Its only for FASTER access to get files. If that was the case, then RAPIDSHARE IS JUST A HUB OF Illegal downloads, brothers..
It is also a best practise to keep sharing (uploading)the files once u hv d/loaded it COMPLETELY, coz if every1 just stopped uploading once they had the fiel, then there will be NO active users available with a COMPLETE COPY of that file.
THe Bottom Line is: DO NOT BE SELFISH and JUST be a LEECHER, Be a SEEDER too..
CHeers n e-peace....