The App Subtitle is located below the App Title in the Product Page Header.
In the iOS 11 App Store, the App Subtitle serves as an additional asset developers can use to describe their app and encourage users to download. Apple also indexes keywords found in the App Subtitle. Hence, it is another asset that developers can use for search optimization. The Subtitle also appears in the Search Results Page, as well as Top Charts & Categories placements. When Developers do not input a Subtitle for their app, the Subtitle will be replaced by the Developer’s name in the Product Page, and the Subtitle will be replaced with the app Category in the Search Results Page and Top Charts & Categories placements.
In the Google Play Store, the App Subtitle is restricted to the developer’s name.