(iPhone 13 or Samsung Galaxy S22+..)
e.g. iOS 15 or Android 10.0 etc.
You can check which version you have installed at the bottom of the Settings menu (to get there just tap the gear icon on the top right corner of the "Plan" tab). The app version is always in this format: X.X.X / vXX (e.g. 1.4.2 / v26).