How Events Originate

However regardless of which event handling methodology you use, the origin of events is still the same
When a user presses and releases the mouse button over a widget like a button, the windowing system of the computer is notified that the mouse button was pressed and released.
The windowing system determines which window the mouse was pressed over. If it is your program's window, it sends the mouse event to your program. However, the windowing system only knows about top level windows. It does not know anything about java controls, dialogs, or buttons. Thus the windowing system notifies your program and lets your program handle things from there.
It's then your program's job to determine what components are notified of the event.
If the mouse is pressed and released over an OK button for example, the program sends mouse-down and mouse-up events to the OK button object. The button looks at these events and determines if it should generate its own event in response. Thus, if the user clicked on the "clickable" area, the button, the button will generate its own "action event" which is the event that you want to handle to perform an action when the OK button is pressed.

Events
Table of Contents
Listening For Events with the 1.0 Model