Event dispatching thread

The event dispatching thread (EDT) is a background thread used in Java to process events from the Abstract Windowing Toolkit (AWT) graphical user interface event queue. These events are primarily update events that cause user interface components to redraw themselves, or input events from input devices such as the mouse or keyboard. The AWT uses a single-threaded painting model in which all screen updates must be performed from a single thread. The event dispatching thread is the only valid thread to update the visual state of visible user interface components. Updating visible components from other threads is the source of many common bugs in Java programs that use Swing.

Reference:
http://en.wikipedia.org/wiki/Event_dispatching_thread