Pretty sure that it's: When you want to go on a wikipedia article, it requests the file from other peers in the network using the bittorrent protocol. It's a copy of Wikipedia placed on bittorrent, presumably with some semantics for article updates.

It looks like it uses a single Wikipedia dump from over a year ago. Would be cool if it supported deltas somehow, so the network doesn't split when a new dump is used.

Bittorrent doesn't have support for that, but you could publish torrents that just host a full version of all the modified pages.

Found out recently that there's a cool project underway to make a distributed wiki - http://wardcunningham.github.io/.

this breaks the bittorrent.