What is it again?

Google AdSense is a fast and absolutely ridiculously easy way for people with websites of all types and sizes to put up and display relevant Google ads on the content pages of their site and earn money.

Because the Google AdSense ads relate to what your visitors came to your site to read about, or because the ads match up to the interests and characteristics of the kind of people your content attracts, you now have a way to improve your content pages AND make some serious bucks off of them.