An event is a CLIM object that represents some sort of user gesture (such as moving the pointer or pressing a key on the keyboard) or that corresponds to some sort of notification from the display server. Event objects store such things as the sheet associated with the event, the x and y position of the pointer within that sheet, the key name or character corresponding to a key on the keyboard, and so forth.
Common Lisp Interface Manager 2.0 User's Guide - 7 Aug 2017