AdSense is Google’s program which allows you to sell space on your website to host other people’s advertisements. Hosting AdSense ads on your website or blog is completely 100% free to you as the host and a great way to earn some money.
How do you earn money with Google’s AdSense? Simple, every time someone clicks on an AdSense ad on your blog Google pays you. Someone clicking on your ad is called “click through.” Your visitor is clicking through your webpage to another webpage via the AdSense link on your website.
Google pays you for these click-through visitors because their advertising has successfully reached a visitor on your blog. You get paid because you agreed to host the ads and you provided good content which got a targeted ad and a resulting click on that ad. google.com