Retargeting ads (see similar, Google Remarketing) entice a user to visit a site by taking into account the user’s past web history. When a user visits a website, a retargetting campaign cookie is attached to the visitor, taking note of what pages and products the user visits while browsing the site.
Once the user leaves the advertiser’s site and begins journeying to other websites, targetting ads can be made to appear in certain ad spaces, displaying ads that specifically call out what the user was looking at on the advertiser’s site earlier.