- A customized ad shown to users who already have the app in order to drive them back to the app
- An app extensions which shows a link to your app below your ad
- A templated “engagement” image ad which allows you to add more text or information to your ad
Explanation: Mobile app engagement campaigns are a great choice for advertisers focused on getting people who’ve installed their app to try the app again, or open it and take specific action. These ads allow flexibility for counting conversions, bidding, and targeting.
Read more here: https://support.google.com/partners/answer/6209162