What is a self-transitioning state, and how is it different from the simpler, caller-driven use of the State pattern?

In the caller-driven form, external code explicitly decides which state is active, for example by calling a setMode() method with the state it wants. In a self-transitioning state machine, the current state object decides on its own, as part of handling an event, what the next state should be — for instance, a media player's StoppedState can call player.setState(new PlayingState()) itself when pressPlay() is handled, so the caller never picks PlayingState directly. This self-transitioning form is closer to how state machines are usually described in theory, since the rules for what comes next live inside the states rather than in the caller. Both are legitimately the State pattern; which one is appropriate depends on whether the 'what happens next' logic genuinely belongs to the object's own internal rules or to an external decision-maker.