Knol is a new Google service created for sharing knowledge. The service has been announced in December 2007 and it's now publicly available.
Knol has much more in common with Squidoo and HubPages than with Wikipedia. The service is centered around authors: each Knol article displays the name of its author and links to a small biography. Google even lets you verify your identity, but this only works if you live on the US.
Knol doesn't intend to become an encyclopedia, so there's no single article about a topic. An author can write about almost any topic, but it's recommended to write authoritative content.
There are three levels of collaboration in Knol:
* open collaboration (any Knol user can edit the article)
* moderate collaboration (any Knol user can suggest changes to the article - enabled by default)
* closed collaboration (only the co-authors can edit the article)
Google uses a rich-text editor borrowed from Page Creator, so it's much easier to edit knols than Wikipedia articles. Users can rate the articles, add comments and write reviews, much like for scholarly works.