Laser rangefinders—whether golf-specific models or not—are complex units that work in a simple way. Laser rangefinders use light beams to calculate the distance to your target. When you push the button, usually located on top of the rangefinder, it sends out a light beam to the target, which is then reflected back to the rangefinder. The rangefinder calculates the time it took the beam to get to the target and back, then calculates the total distance based on that time. While it’s a fairly complicated formula that uses the speed of light and other such intricacies, you don’t really need to know that. All you need to know is the exact distance to the pin, and good rangefinders give you that calculation within a yard or less.