Android OS developers announced the transition to a new format of applications and games in the summer of 2021. The official Google blog warns about replacing the usual software extension APK with AAB.

The Android App Bundle (AAB) was introduced back in 2018 and it is this format that software developers have gradually switched to. The essence of the innovation is that now Google itself is engaged in the optimization of various versions of the application, "packing" them into a container. The user will not be able to manually install the AAB file itself on the smartphone, as was the case with the usual APK files. This will increase the security of applications, but also negatively affect the "openness" of the Android platform.

Google has planned to completely switch its Google Play app store to AAB format in August. It is said that users will benefit in the amount of software that will take 15-20 percent less memory on the device.

https://developer.android.com/guide/app-bundle