A pointing device is any hardware component that allows a user to input spatial data to a computer. CAD systems and Graphical User Interfaces (GUI) allow the user to control and provide data to the computer using physical "gestures" - point, click, and drag - typically by moving a hand-held mouse across the surface of the physical desktop and activating switches on the mouse. Movements of the pointing device are echoed on a graphical representation of a desktop on the screen by movements of the mouse pointer and other visual changes.
While the most common pointing device by far is the mouse, other kinds include trackball, touchpad, pointing stick, lightpen, various kinds of digitizing tablets which use a stylus, and even a special "data glove" that translates the user's movements to computer gestures.
"Pointing device" can also refer to a special "stick" (sometimes telecopic, to reduce the length when not in use), or a lamp with a narrow light beam that is pointed at a map, blackboard, slide screen, movie screen, etc.; sometimes the light is in the form of an arrow.