Ad Links are a new form of text advertising that we're offering to our AdSense publishers. Using the same contextual targeting algorithm that targets Google ads to your content pages, Ad Links units display a list of topics that are relevant to your page. Each topic, when clicked, brings the user to a page of related advertisements", — this is how Ad Links are defined by Google.

According to Google, you are allowed to put max. 3 Adsense codes. But experts say that displaying too many Adsense ads in a page distract the attention of the visitors and they lose interest in the site. Therefore it's always advised to put only one Adsense code and that too close to the main content of the page, to get the best results.