Macinstruct has placed a great article on-line that explains, in simple terms, just what that whole Gnutella thing is all about. (Not to be confused with Nutella, the better-than-sex wonderspread!) To oversimply to a nauseating degree, it's how you'll snag MP3's (and whatever other kind of file, actually) when Napster gets shut down. A look at the Mac client, Mactella is included as well. Informative stuff.