For the button tutorial, you say you don't know what "hit" means. Well, here is the definition. The last frame, labelled "Hit" is special. It is simply used to specify the area that triggers mousevents. If you leave this frame blank - then mouse events will be triggered when the mouse moves over the visible button. But if you draw an area that is bigger than the button - then the mouse event will occur as soon as the mouse gets even close to the button. On the contrary you can draw an area that is smaller than the button, so that mouse events are only triggered when the mouse is at the center of your button.
However, the real power of the "Hit" frame is a bit more sophisticated. If you draw something in the hit area that is outside the area covered by the visible button - then the button will react to mouseevents in the Hit area. That means that you can make something happen on one part of the screen when the user moves the mouse over another part of the screen.