These are data files containing the game's graphics and media. They must be placed in Android/obb/ for the game to run.
Android blocks installations from "Unknown Sources" by default to protect you. Here is how to safely bypass that: mobile game apk download
Get your hands on "unreleased" builds to see new features before anyone else. 3. How to Safely Install an APK (Step-by-Step) These are data files containing the game's graphics