https://en-gb.facebook.com/business/a/online-sales/facebook-…
In a nutshell, if someone wants to do retargeting, then they can use Criteo’s demand side platform. Criteo is one of Facebook’s apprved DSP solution.
By using Facebook Exchange, you can target people to see an ad based on other things they have done on the Internet using a demand side platform that you use across other display networks and exchanges.
Anirban