Facebook shows ads based on information we have about you and your activity, such as Pages you and your friends like, information from your Facebook and Instagram profile, the content you create or interact with across Facebook and Instagram and places you check in to using Facebook. We may also use information we have about others and their activity to show you more relevant ads. If personalized ads based on data about your activity from partners are allowed, we can also use data like your activity on websites off of Facebook to decide which ads to show you. Source: Facebook.com