For a start, the image that thibran posted could be fixed. It isn't consistent about whether the bordered rectangles represent represent onFoo() calls or the state after their calls.

The page it comes from says « the colored ovals are major states the Activity can be in ».

There should be a coloured oval for the (rather common) state where the Activity is the background after onStop(), and the two arrows coming out of onStop() should come out of that oval.