Tony,
It would appear that the web site uses "torrent" technology to distribute the backing tracks. Long story short: the "torrent" will look for other online computers that have the requested tracks installed - and will suck the data from them, rather than going all the way back to the original distributor. Of course, once you install a few popular tracks you will be expected to do your share and contribute what is on your computer.
Sounds like it may be just a bit too "communal" for your tastes.
