Exchange is/was FB's retargeting/remarketing solution, AKA "we will follow you everywhere you go on the Web and remind you that you once looked at a pair of sho

Exchange is/was FB's retargeting/remarketing solution, AKA "we will follow you everywhere you go on the Web and remind you that you once looked at a pair of shoes on our site." Some detail would be cool -- adtech is intrinsically interesting, if ethically somewhat murky.