Definition: These days, not much -- at least not for the average computer user. Optical and laser mice differ by the types of technology they use to track movement. The optical mouse uses an LED light to track movement, while the laser mouse, as its moniker indicates, uses a laser.
Laser mice have a higher dpi, which means that they can track more dots per inch, which in turn means that they're more sensitive. But while this may have been an issue in the past, both optical and laser mice are now able to hit high dpi marks, and your average user will never notice the difference. Gamers and graphic designers may still perceive one and have personal preferences for a device.
