Whenever an event (like click, mouseover, mouseout etc) occurs, the relevant data about that event is placed into the event object. For example, the event object contains event data like, the X and Y coordinates of the mouse pointer when the event occurred, the HTML element that fired the event, which mouse button is clicked etc. Obtaining the event object is straightforward. The event object is always passed to the event handler method. Let us understand this with an example. When we click the button, we want to capture the following event data 1. Event name 2. Mouse X coordinate when the event occured 3. Mouse Y coordinate when the event occured 4. The control that raised the event 5. The HTML tag name that raised the event Notice that in the example below, we are passing event object as a parameter to the event handler method. The type property gives us the event name that occured. clientX and clientY properties return the X and Y coordinates of the mouse pointer. Target property returns the HTML element that raised the event.