What is the 9 ball billiards Offline / Online pool free game game, how does it work?

According to the introduction of Pool 2020, 9 ball billiards Offline / Online pool free game is a Sports game on the Android platform. There is currently a 78.13 version released on Feb 21, 2020, you can see the details below.

Cue sports (sometimes written cuesports), also known as billiard sports, are a wide variety of games of skill generally played with a cue stick which is used to strike billiard balls, moving them around a cloth-covered billiards table bounded by rubber cushions.

Make sure that third-party apps are allowed on your device: go to Menu->Settings->Security-> and check "Unknown Sources"

Tap the APK file. Allow the app any required permissions it asks for. Then, at the bottom of the installer window, click INSTALL.

You'll see a confirmation the app is installed. Now you'll see the app available in your list of installed apps.