Both laser and optical mice technically shine a light off a surface and measure the reflection in order to provide precision tracking. An optical mouse usually uses an infrared LED (sometimes photodiodes), while a laser mouse uses a laser to illuminate a surface.
Optical sensors have less than a one percent variation in tracking at different speeds, while laser mice can have five percent or more variation. An optical mouse works well on a mouse pad or any non-glossy surface. A laser mouse will work on any surface.