Actions consist of a trigger event, a message and a target.
The trigger event is what happens or what you do in order to begin your action or chain of actions. The target is the object to which the message is sent. Sometimes the trigger event is placed on the target, but it can be anything from a mouse click or a page load, to another action completing elsewhere on the page. All actions are created through the use of the CSS and Layers specifications in HTML 4.0 and JavaScript or Jscript. You can also create your own actions in other scripting languages if you desire.