There are two types of marketplaces. Open marketplaces and private marketplaces. Available open marketplaces don’t offer much control to the publishers, but more and more private marketplaces provide higher security and control to the publishers. Publishers can control who can advertise over their platform, select the bidders as per their preference, select the floor price, and other unique and specific controls as well.
Private marketplaces are much safer than open marketplaces and offer much more control to the publishers over what they can advertise on their platforms and control it to the granular level. Generally, private marketplaces are safer for large publishers with big audiences.
Read More About What is google adx