Events are actions which can be detected through JavaScript.  An example would be the on Mouse Over event that is detected while the user moves the mouse on an object.  Another event is the onLoad even that is detected as soon as the page is finished loading.  Generally, events are utilized in combination with functions, so that the function is called while the event happens.  An instance would be a function that would animate a button. The function shifts two images simply. One image, which illustrates the button in an "up" position, and another image that illustrates the button in a "down" position.  If this function is called using an onMouseOver event, this will make it look as if the button is pressed down while the mouse is moved over the image.