GDNGDN (Google Display Network) - The Google Display Network is the world's largest display advertising network for placing banner ads on Google web properties (such as YouTube, Blogger, Gmail,(...)
IDFAIDFA (Identifier for Advertisers) - Opt-out tracking and targeting tool for mobile applications.
Impression An impression is generated every time an end user views an ad.
In-App AdsIn-App Ads are mobile ads that appear within a mobile app. This can include standard banners, video and rich media ad formats.
For more information about In-App Advertising click here.