A Google AdSense is a free, simple way to earn money by displaying targeted ads next to your online content. With AdSense, you can show relevant and engaging ads to your site visitors and even customize the look and feel of ads to match your website. Google AdSense provides a way for website owners to earn money from their online content. AdSense works by matching text and display ads to your site based on your content and visitors. The ads are created and paid for by advertisers who want to promote their products. Since these advertisers pay different prices for different ads the amount you earn will vary. (Source: www.google.com/adsense/)