Many smartphones and tablets use Android OS these days.
If you have an android based phone and you want to check what version of android is installed on your phone, then here’s the procedure.
Press Home button, and then the Menu button on your android phone. Then press Settings button. Swipe up a bit to scroll down and press About Phone. Look for the line that says Firmware version or Android version. The version displayed here is the version of android OS installed on your phone.