There are two types of ad sources you can set up in your account: bidding ad sources or waterfall ad sources. The type of source you set up determines how the ad source bids for your impressions. Bidding sources place bids in real-time and compete in a single auction, while waterfall sources are called individually in the order of their eCPM, which is set by you.
You can also set up a custom event. Custom events let you set up waterfall mediation for an ad source that isn't supported by AdMob.
Learn how to:
