1. Hide virtual keyboard if shown

2. Go to previous app view. This is app-dependent though it will probably, successively with each press:

a. Close menus if open (context, sidebar, etc)

b. Go to previous (web)page if web/file browser c. Go out of submenus (ex: settings/WiFi -> settings) if not in a browser or if the oldest page has been reached. Keeps walking the tree upwards.

3. Reach the main app view (usually the one you land on when opening the app)

4. One more press minimizes the app.

It is fairly consistent, but some apps decide otherwise:

* some will minimize as soon as you press it (I've seen games do it)

* some will open a new menu (again, games: pause menu)

* some will seemingly walk you the history of visited pages instead of the hierarchy -- which may make sense but can be confusing

* some old apps will display a toast "press back twice to exit". This used to be common back when physical buttons were the norm, but I haven't seen this message a lot.

So, mostly consistent with some weird-behaving apps. Same as on desktop I guess?

Back means the previous screen.

If you're in Chrome, the previous entry in the history. If you're in YouTube, the previous video. If you were previously on the main screen and you just clicked into an app, the main screen.

What's confusing about it? Seems very intuitive to me, it's like CTRL+Z, it always changes what it does but the behavior is to undo the latest action.