Happening of something is known as an event.
JSF event handling:
In JSF when a button is clicked or change value in text filed etc then corresponding JSF component create an instance of the corresponding event class and adds the event to the event list. After adding the event in the event list JSF component call the corresponding listener or handler method.
Note: JSF also provides the facility to handle the application level events which happens when application start or stop.
|JSF fired value change events when user make changes in input components.|
|JSF fired action events when user clicks on a button or link component.|
|JSF fired application events when application start or stop or during JSF lifecycle: PostConstructApplicationEvent, PreDestroyApplicationEvent, PreRenderViewEvent.|