BitTorrent is definately a peer to peer program. But what makes it special is it's ability to take advantage of everyones upload bandwidth. A very large file is broken up into small chunks. As you download a section and it completes, then you then can upload this segment to another one that is requesting the same large file and also needs that piece. Then that person will share his copy. Meanwhile everyone is downloading other bits. Therefore demand creates the scale of the network and it frankly is limitless. In addition, the more you upload, the faster you can download. Once the files are complete the temporay and spontaneous network ceases to exist. This is what scares the crap out of movie moguls. This is also why the Tracking sites are under attack as they are a static target for the authorities.
In my humble opinion though, they are not doing anything illegal by providing links to copyrighted material. Due to the failure (so far) in the United States to pass the so called INDUCE Act. This is where you are guilty if you just help someone to commit an illegal act. (basically) But we are all anxious to see what happens to these sites if they come under legal scrutiny in the meantime.
However, having said that. You can imagine what a savings in bandwidth this can be for say Linux developers to distribute a new version. No central server under the strain of thousands of downloaders. Here is a nice explanation of how BitTorrent works. It must not be taken away from us for it may well be needed in the future for legal file sharing of copyrighted materials. Sort of a iTunes for movies let's say. It is an extremely effective program for file distribution that is difficult to monitor or control.