There could be no two opinions about the popularity of AdSense for putting up ads on the websites both for channeling more traffic and creating the Business Link On Marketing. Normally, such AdSense uses the JavaScript code to put in the ads into a site that is participating with it. Moreover, when such ad is put on, the search engine will first check whether or not the site has been visited by the Mediabot.
If the site is not visited by Mediabot, the ads may be displayed as those put up for charitable causes. Such charitable ads are also known as Public Service Announcements or PSA. You may not confuse Mediabot with Googleboat that helps maintaining Google’s search index for managing the Pay Per Click Marketing.
Sites use AdSense to monetize their contents while the webmasters try to maximize their income through it. A wide range of activities and methods to generate larger traffic is employed by them. The contents on the site are built up in such a way that would attract AdSense ads that generates revenue per click. You may look at the AdSense information for more information on the topic.
One interesting feature is that many websites use copies of contents that are well accepted by AdSense instead of setting up their own unique website. AdSense may refuse certain contains that is direct and hence following attractive lines displayed by others have become an important feature of Pay Per Click Advertising.