An LED (light-emitting diode) is a device that emits light when an electric current passes through it. This phenomenon, called electroluminescence, differs, for example, from incandescence, in which light is emitted as a result of heating, and chemoluminescence, in which light is emitted as a result of chemical reactions. The color of the light emitted by an LED depends on the semiconducting material used, and can be in the infrared, visible, or ultraviolet ranges.

An LED is a type of diode that composed of a semiconducting material, a lead frame, and a covering of epoxy resin. The semiconducting material contains impurities that create a structure called "p-n junction". When current passes through the LED, the material of this junction will react and emit light. The epoxy covering angles the light emitted from the semiconductor and makes the LED be tough, durable, and resistant to the elements. An LED contains no loose or moving parts.

Unlike traditional incandescent bulbs or fluorescent lamps, LED lamps produce the light without undesired heat or energy losses. Additionally, the solid state operation of LED (i.e., independent of gas or vacuum tubes) provides greater resistance to shock, vibration and wear, thereby increases their lifespan significantly. LED lighting has been described by the United States Department of Energy as a pivotal emerging technology that has a promising future.

Some of the advantages of LED include：
a.Energy saving – LED is 10 to 50 times more energy efficient than incandescent light bulb and reduces operating costs up to 90%。
b.Long lifespan – While most incandescent light products are only rated up to 3,000 hours, LED luminaires are up to 100,000 hours, or
    more than 10 years of continuous use.
c.Safety – Low-voltage power consumption and low heat output enhance operational safety and make LED luminaire cool and safe to
    touch during use.
d.Durability – LED lumianires are more durable than conventional bulbs and more resistant to breakage, failure, vibration, shock and temperature extremes.
e.Small size – High intensity, low weight and small volume that make luminaire design more flexible. f.Instant response – No flicker, just
    pure dramatic light.
g.Quality light output – Minimal ultraviolet or infrared radiation.