Advertising networks (including Facebook and Google) select the advertisements from their catalog to display for a particular user and page (based on informatio

Advertising networks (including Facebook and Google) select the advertisements from their catalog to display for a particular user and page (based on information that they have on the user, the page, and the advert and competing adverts). At no point is the advertiser ever given identifying information about particular users, although demographic/summary data may be provided.