Retargeted ads allow a business to show targeted ads to people who visited a website but didn't make a purchase, with the hopes of luring the user back to make a purchase. For example, if you're shopping on Website A for a new couch but don't buy one, you may see retargeted ads while on Website B for the couch you were viewing on Website A. Retargeted ads work by using cookies to store and then remember data about website visitors.