I just found out about it the other day. Its literally p2p file sharing. You can let people visit designated directories on your local file system and go visit theirs. Its fast and personable. They even have an AOL IM thing going on. I found out about it because they've got a lot of music and its relatively difficult to find good music torrents. I thought it was basically transmission or another torrent client, but its totally different. Linux Mint has the FOSS client Nicotine+ in their repository. The whole process was quick and easy. Find me there under the same user name.