Knol is Google’s answer to Wikipedia – a replica of Wikipedia, but with a few differences. According to Google, a knol (is not a War3 creep) stands for a unit of knowledge - just think of it as a Wiki!

Our goal is to encourage people who know a particular subject to write an authoritative article about it. The key idea behind the knol project is to highlight authors. Books have authors' names right on the cover, news articles have bylines, scientific articles always have authors -- but somehow the web evolved without a strong standard to keep authors names highlighted. We believe that knowing who wrote what will significantly help users make better use of web content. At the heart, a knol is just a web page; we use the word "knol" as the name of the project and as an instance of an article interchangeably. It is well-organized, nicely presented, and has a distinct look and feel, but it is still just a web page. Google will provide easy-to-use tools for writing, editing, and so on, and it will provide free hosting of the content. Writers only need to write; we'll do the rest.

Basically, it’s the same thing as a Wiki EXCEPT knol is paired with Google AdSense & is more author-centric…. Authors can show their pictures, log-in with their gmail account, etc.

A unique element of Knol is its ad system, Google says. While ads will be strictly optional, an author can choose to have context-sensitive AdSense ads appear on their article and will collect some of the revenue from each ad, potentially serving as a source of income for active and popular authors.

After the YouTube ads, this seems another major source of revenue for Google and AdSense users who love to write!(I’m starting to suspect that Google made this whole Knol thing just to cash in on AdSense…) However, I’m still intrigued about how multiple authors will be able to profit from a single article? Maybe their ads will be rotated…

A knol on a particular topic is meant to be the first thing someone who searches for this topic for the first time will want to read. The goal is for knols to cover all topics, from scientific concepts, to medical information, from geographical and historical, to entertainment, from product information, to how-to-fix-it instructions. Google will NOT serve as an editor in any way, and will not bless any content. All editorial responsibilities and control will rest with the authors.

Although Google says it won’t tamper with the content - vandalism may force Google to at least enforce an automated moderation system – just like with Wikipedia.

Google Knol seems to be far more “serious” than Wikipedia (like a normal encyclopaedia should be) since it’s more structured and professional looking. & I find the comments section really very interesting – it seems that Google is doing a 2-in-1, a Wiki & a blog?

The rating system seems to be a more practical approach towards maintaining a required level of high quality content (low rated content will eventually be edited & so on…).

No need to search for Knol on the internet, it’s not online for the time being. Google Knol is currently available only as part of an invitation-based system…. It’s still in the beta stage - & don’t forget Google betas remain betas for ever… like Gtalk! (I’m still searching for those very hard to find invitations!)

As a sidenote, just like Gizmodo pointed out… Google seems determined to be omnipresent everywhere! (Android, Google Apps, Gmail, Blogger, Orkut, Knol, Gphone, 700 Mhz spectrum, Earth, Mars…)

More info:
Gizmodo
Electronista
Official Google Blog: Encouraging people to contribute knowledge
BBC News - Google debuts knowledge project