The CCDirector is the component which takes care of going back and forth between scenes.

The CCDirector is a shared (singleton) object. It knows which scene is currently active, and it handles a stack of scenes to allow things like “scene calls” (pausing a Scene and putting it on hold while another enters, and then returning to the original). The CCDirector is the one who will actually change the CCScene, after a CCLayer has asked for push, replacement or end of the current scene. 

The CCDirector is also responsible for initializing OpenGL ES.