An LED, or light-emitting diode, is a semiconductor that emits light when activated with a suitable voltage. Electrons recombine with electron holes at the p-n junction to release energy in the form of photons, an effect called electroluminescence. Modern LEDs are able to use this effect to emit light across visible, ultraviolet and infrared wavelengths, all with very high brightness.
Advances in semiconductor technology have led to LEDs suitable for environmental and task lighting, and new types of displays and sensors. They hold many advantages over their incandescent and gas-discharge counterparts, including vastly lower energy consumption, longer component lifetime, increased durability, smaller sizes, and faster switching. Increased energy efficiency allows the LED to emit many more lumens than a similarly sized light source of a different type, and at a much lower cost.