What moves the mouse pointer?

Answer 1

In a ball mouse, the ball, which is moved by contact on a surface, has three directional roll sensors which transfer electrical signals to the computer which then moves the mouse pointer on the screen. In laser and optical mice, the roll sensors are replaced by lasers or infrared sensors, which detect which direction the mouse is moving. This is sent to the computer which moves the mouse pointer. Laser and optical mice are more accurate than ball mice, but don't work on reflective or transparen surfaces such as foil or glass, which is not a problem for ball mice.