I use utorrent on occasion.
The facts (as far as I know which ain't much)
Seeds: The computers feeding the download
Peers: The computers d'loading at the same time
When you download, you also upload & seed others.
The d'load speed is dependent on the # of seeds, # of peers & the speed of everybody's internet connection.
Here is a screenshot of a d'load I just fired up to show you:
Ian