A trackball is a computer pointing device which can perform the same functions as a mouse. Computer mice have small balls inside of them, and when a user moves the mouse, the ball rolls, causing the pointer on the screen to move. With a trackball, the user simply rolls the ball itself using her fingers or thumb, while the body of the device stays in place. Although the devices can be used for identical tasks, a trackball can sometimes offer distinct advantages over a mouse.
Small, soft or uneven surfaces
Trackballs can be used where mice cannot. A traditional computer mouse will not function well when not on a smooth, flat surface. Trackballs, by contrast, do not require a flat surface over which to move. They can be used in vehicles, on the arm of your couch, in bed, outdoors, or anywhere you wish to use your computer. This makes them a favorite among laptop users who spend most of their time away from their desks.
When scrolling through electronic books or very large documents, a trackball can be much easier to use than a mouse. With a mouse, you can hold down the left button and pull the mouse down to scroll down through the data. You will, however, eventually reach the edge of the surface or mouse pad, and have to lift the device, move it back up, and set it down again. Since the trackball device itself never moves, it offers an unlimited scrolling area in any given direction. A trackball also often spins very freely, so a simple flick of your fingers will produce a scroll much longer than a movement with a mouse.
Games are another area where trackballs excel. Sports games in particular, such as golf, baseball and bowling games, often read how quickly and how far a user moves their pointing device to gauge the strength of a hit or throw. Using a trackball, which spins very freely, a user can get much more power into their stroke, translating into a much stronger hit or throw in the game.