Although drawing many similarities with Wikipedia in that users post authoritative articles on any given subject, Knol has the author's name at the bottom so you'll know who to email when you find out canoe's weren't invented by George Bush Snr.
Users can add comments and suggestions, though the author has to approve these before they go live.
Ads make sense
Google has also allowed users to include ads from the Adsense program, so can get some revenue share from click-throughs.
To illustrate each article, Google has struck a deal with the New Yorker magazine to supply one article from its cartoon library, so each article will look funny if you haven't got the picture to match.
Go to knol.google.com to type up that article on mugs from Swaziland you've been dying to write.