Google's AdSense for Content automatically delivers classified-style ads that are relevant to your audience and your site content.
Often these ads are so well-matched to your niche and your page topic that your readers find them to be a genuinely useful resource.
Once your account has been approved by Google, putting the ads on your site is easy.
You simply choose the details of how you want your site's AdSense ads formatted, then copy and paste some javascript into your page's HTML - and voila, you're serving up ads.
Whenever someone clicks on one of the AdSense ads on your site, you earn anywhere from a few cents to several dollars, depending on the value of the ad's main keyword.
For publishers, serving AdSense ads on your site is one of the easiest ways to monetize.
There are positives and negatives to placing AdSense ads on your site. You may want AdSense in some areas of your site but not in others.
Important: Read the AdSense Program Policies.
Visit the AdSense Information Center for tips, FAQ, and signup.