A trackball is a computer device that serves as an alternative to a computer mouse or touch pad for moving the pointer around on a computer screen.
Function
A trackball consists of a stationary hand rest, which is usually larger than a mouse, that contains a round track ball set in a socket, which allows it to rotate freely. You rotate the ball with your thumb, and sensors detect movement along two perpendicular axes, which, in turn, move the pointer on the screen.
Similarity to a Mouse
The basic principle of a trackball is the same as a ball mouse: with a ball mouse, moving the mouse causes the ball on the bottom to move, and sensors pick up the movement. With a track ball, the thumb moves the ball directly instead rolling the ball across a flat surface.
Movement
Trackballs are useful because the hand can remain stationary while using them, so they are easy to use without a flat surface or mouse pad.
Accuracy
Trackballs tend not to skip and flow more smoothly than mice or touch pads, but mice are often easier to manipulate quickly and accurately.
Maintenance
Trackballs tend not to get as dirty as mice because only the thumb comes in contact with the ball. The trackball is easily removed and can be rubbed clean with a piece of cloth
