The objective of such ads is to drive mobile app installs. Facebook App Install Ads help app owners increase the number of users by letting people effortlessly download the app within a few clicks.
Advertisers can select two objectives for their campaigns: App Install Ads and App Engagement Ads. App Install Ads help people find the app and download it from the app marketplace. App Engagement Ads help advertisers bring existing users back to the app or motivate people to take a specific action in the app.