What is an app engagement ad?

What is an app engagement ad?

A customized ad shown to users who already have the app in order to drive them back to the app
A templated “engagement” image ad which allows you to add more text or information to your ad
An ad which uses cookies to appear to users who have already downloaded an app
An app extension which shows a link to your app below your ad

Answer is – A customized ad shown to users who already have the app in order to drive them back to the app