A little ball underneath a mouse is what provides motion of the cursor. Notebook computers usually have the mouse built-in to the keyboard as a small rubber dot that you can move 360 degrees, or as a touchpad or trackball. Optical mice are pointing utensils that look like normal mice except without a ball. New optical mice can glide smoothly on any surface, not just your mousepad. Because optical mice have no ball and no moving parts, you really don t have to worry about cleaning the unit.
Some optical mice come with a built-in scroll wheel.
Apple has the Apple Pro Mouse, which basically has no ball and no buttons. The whole mouse is a super sensitive button. Trackball cursor controls operate much like an inverted mouse. Instead of moving the mouse with your hand, the trackball allows you to move the cursor by rotating a ball with your fingers. With desktop computers, trackballs are fairly large for easier maneuvering and come sitting inside some kind of a holder.