Android (AOSP) is an operating system for phones and tablets; may also contain the proprietary Google Media Services (GMS). You might want one of my topics:

Android Versions

For developers, the relevant SDK vs public Android versions are:

In 2023 you would typically target at least 21 because otherwise intent timers and some other useful APIs would be missing.

Android Variants

If you want to get off Google Android, your alternatives are:

And with that, good luck and have fun!

EOF (Aug:2023)