What is audio focus in Android class AudioManager?

It has to do with priority when using the speakers, to prevent playing many things at once or being overridden. If you requestAudioFocus(), you're declaring that you want control. You can then listen with onAudioFocusChange(int focusChange) to see if anything else tries to play a sound. You may forcefully lose focus (like during a phone call) but then you can gain it later. You should abandonAudioFocus() when you're finished.