How DoubleClick Ad Exchange works

DoubleClick Ad Exchange is a real-time marketplace partnered with the Google Display Network for buying and selling advertising. It represents another market for advertisers to bid on display advertising across the Internet. When you have a campaign that targets the Display Network, you automatically have access to Ad Exchange publisher sites that comply with AdWords' guidelines.

If you go butterfly hunting during the height of summer, the bigger your butterfly net, the more butterflies you'll be able to catch. The same goes for your customers: if you use a wider net, you might be able to capture customers from high-traffic parts of the web that weren't previously available to you. That's why showing your AdWords ads on Ad Exchange publisher sites can help you bring in new customers that you weren't able to reach before.

Here's how it works:

As long as you've targeted the Display Network for your campaign, your ads can appear on Ad Exchange publisher sites, in addition to those available through Google AdSense .
While your potential reach on additional publisher sites expands, the AdWords targeting, reporting, and other account processes you're already familiar with remain the same.
Ad Exchange publishers who want to display Google AdWords ads must adhere to the Google AdSense program policies.

https://support.google.com/adwords/answer/2472739?hl=en