Infolinks is an in text advertising network that serves pay per click ads on a publisher blog/website. It is considered as one of the highest paying advertising networks, especially for bloggers who do not have extra space to displays ads.
Infolinks ads are displayed as double under links that target specific words in page. So, whenever a reader hovers his mouse over specific words, a relevant word is displayed and if he moves the mouse away, the ad disappears. If the reader clicks on that particular link, he is taken to the advertiser’s page and you get paid in return.