Knol is Google's new Wikipedia, where anyone can post their own articles (also known as knols).
To start making money, you need to create a knol. To do this you will need to sign in with your Gmail account or create a new one. Then you will need to register with adsense, which is google's ads publishing program. Now, once you have published a knol and adsense ads are enabled, relevant ads will appear next to your articles. When people read your articles and click on your ads, you will get paid for each click.
How much Money can I make?
It all depends on how many times your ads are clicked and what the topic of your article is. For example, if your article is about health insurance you'll get more money per click than an article about free wallpapers. So start writing articles about different topics, to see which can earn you the most money.
If you take advantage of your articles, you'll find it possible to link to your own website or blog. Which can easily give you lots of quality traffic to your site.