This is one of the largest advertising programs available to web publishers. In Google's own words:
Google AdSense matches ads to your site's content and you earn money whenever your visitors click on them.
It really is as simple as that. AdSense is a straightforward way of introducing advertising to your blog. It may not be the most profitable form of advertising, but it can generate a steady income stream.
As with most Google applications, AdSense has plenty of advanced features. Most of these are beyond the scope of this chapter, but we will run through a quick-start guide for getting AdSense on your blog. Once you have it set up, you can explore the more advanced features with the help of Google's excellent documentation (http://www.google.com/adsense/support/).