Initiates when a mouse click occurs within the region. When a click event initiates for a text or numeric field, calculations or scripts execute immediately. However, the value of the field does not change in response to calculations and scripts until the field loses focus.
Note:
You cannot place a calculation or script on the click event of a submit button because the calculation or script will override the submission action. Instead, place any calculations and scripts on the preSubmit event for a submit button.

For more information about form submission actions, see the LiveCycle Designer ES Help.

Use this event for performing an action as a direct response to a form filler clicking a button or selecting a radio button or check box on a form. For example, you can use the click event for a check box to hide and show a field on the form.
See also 

click event