When they use laser, it's usually invisible. It uses a highly precise laser to "track" the surface you're using. And they're way more accurate on any surface than optical mice are. The downside is the price. Laser mice are expensive, but if you can afford it, get one.
Optical is different. It uses a red light to shine on the surface and relflects back to the sensor in the mouse. Usually optical loses tracking on metal surfaces or surfaces that have different reflectiveness. However, optical is cheap now and is easily bought. If you're on a budget or just need something good but not super-good, then get optical.
Logitech, Microsoft and Razer make extremely nice optical and laser mice (although Razer only makes wired mice).