Google Certified Ad Networks is a new feature which will allow non-Adwords advertisers to compete for ad units in publisher websites. Which means the higher paying ad will be displayed, you can generate the most profit for every ad unit displayed in your website.
Google-certified networks are similar to AdSense, they’re the companies who buy and sell ads on sites they don’t own themselves. To get the quality of ads Google certifies all the participating ad networks to Adsense standards ( ad quality, speed , etc.,).
All Google certified ad networks will adhere to the standard Google AdWords ad format. So, you will get to see the same adsense format of ads from Google certified ad networks.
Reporting and payments
Even though ads will be displayed from other certified ad networks, reporting and payments (Page impressions, Clicks, Page CTR ) will continue to run through AdSense.
Allow/ Block Google certified ad networks
Google-certified ad networks ads will will appear on AdSense pages (adsense publishers website). If you want to opt out any Google certified ad networks to bid on your inventory you can do so it at the Ad Review Center, which has control to allowing or block Google certified ad networks.