Like the title says, event logger is here to keep a track of every events dispatched by an object.
By default, events that are fired many times like enterFrame or mouse events are not selected so as not to pollute the list. If you want to catch it or to remove some others, click on the filters button; events are classifed by type, select any events type you need.
The events can be 'introspected'. Select a row in the list and click on the 'tree' radio button, a view like the one in the object inspector will appear so you will be able to see all the properties of the event.