https://adtmag.com/articles/2018/10/22/android-app-bundle.aspx

Google announced enhancements to its new Android App Bundle publishing format that shrinks the size of app downloads, which have steadily grown to the point they inhibit device installations.

The Android App Bundle format lets developers upload all resources for an app to the Google Play store, which then takes care of delivering just the resources that are needed by a specific user and device. That shrinks the size of APK downloads, whose large size caused many users to not install an app or remove a big app when space is needed for a new one.