Earlier this week Google started inviting a selected group of people to try a new, free tool that they are calling "knol", which stands for a unit of knowledge. Their goal is to encourage people who know a particular subject to write an authoritative article about it. The tool is still in development and this is just the first phase of testing. For now, using it is by invitation only.
Anyone will be free to write. For many topics, there will likely be competing "knols" on the same subject and "Competition of ideas is a good thing" says Google.
"Knols" will include strong community tools. People will be able to submit comments, questions, edits, additional content, and so on. Anyone will be able to rate a "knol" or write a review of it.
Google are quite experienced with ranking web pages, and feel confident that they will be up to the challenge of ranking Knols appropriately.