What is OBB? How does it work?

Google Play requires that the compressed APK that users download be no more than 100MB, Each time you upload an APK using the Google Play Console, you have the option to add one or two expansion .obb files to the APK, can be any format you choose (ZIP, PDF, MP4, etc.). Each file can be up to 2GB and it can be any format you choose developers can use XAPK file format to allow users download the APK file on Android without corruption.

OBB file Storage location & File name format

<shared-storage>/Android/obb/<package-name>/[main|patch].<expansion-version>.<package-name>.obb
What is APK? How does it work?

How can i install in?
If you download by your Android mobile phone. You can install it first. If you install and open it, it still metioned that the obb file is missing.
Try renaming the file within a .zip extension. And Unzip it and copy the .obb file named 'com.gameXXXXXXXX.obb' into required location:
/SDCARD/storage/emulated/0/Android/obb/com.gameXXXXXXXX/

If you download it on your computer, renaming the file within a .zip extension. Unzip it find the .apk file and transfer to your phone and install it. Second, you should build a file on your phone. The location should be:/SDCARD/storage/emulated/0/Android/obb/pacage-name/.
You should build a new file and named after the package name of the apk. Then you should copy the .obb file into the location file.

How can i install it faster, it is too complicated ?!
You can download the app installer help you to install the apk with OBB file. It can help you install app more faster, and it is no need to worry about how to build the apk file.
Also, you can find the best games and apps on it! Come and Download the PlayMods App.