Mechanical: It is used in old PC and has a rubber ball, wheels, and sensors to detect mouse motion. If mouse is moved, rubber ball moves in the same direction, making the wheels supporting the ball spin and whose movement is detected by sensors. The sensors send signal to PC.
Optical: It uses light with a sensor to calculate position change by detecting the change in light given by mouse and the light reflected by surface. There are no moving parts in it.
Opto-mechanical: It is a combination of the mechanical and optical mouse. A rubber ball is used along with a light-sensor. Light-emitting diodes are used to detect mouse movements.