Google AdSense matches ads to your site’s content, and you earn money whenever your visitors click on them. There are two types of ads provided by Google.

AdSense for content

Automatically crawls the content of your pages and delivers ads (you can choose both text or image ads) that are relevant to your audience and your site content—ads so well-matched, in fact, that your readers will actually find them useful.

AdSense for search

Allows website publishers to provide Google web and site search to their visitors, and to earn money by displaying Google ads on the search results pages.

Type: CPC and CPM
Source: https://www.google.com/adsense