What is with the 3rd party cookies?

tribalfusion.com
doubleclick.net
atdmt.com
yieldmanager.com
tacoda.net

Not a complaint or suggestion just a question
What is with them and what purpose do they serve?

Ad servers, referral trackers.

Ad servers, referral trackers.

and... that means... ????

and... that means... ????
They track where you go and what you do in order to determine the effectiveness of their ads. They are "tracker" cookies.