
An action is an incident that can be recognized by the application, for example, choosing a button. When you perform the action during runtime, the event assigned to the action occurs and triggers the corresponding event handler. For example, navigates to the next view when the user chooses the specified button.
When you create an action, the IDE generates an event handler called Action Event Handler for the action. This event handler stores the Java code that is executed when the action or event occurs. You can implement the event handler, as required.
More information: Event Handling