LED is light-emitting diode which is a semiconductor device that emits light when an electric current is passed through it. Light is produced when the particles that carry the current (known as electrons and holes) combine together within the semiconductor material.
Since light is generated within the solid semiconductor material, LEDs are described as solid-state devices. The term solid-state lighting, which also encompasses organic LEDs (OLEDs), distinguishes this lighting technology from other sources that use heated filaments (incandescent and tungsten halogen lamps) or gas discharge (fluorescent lamps).


As solid-state light sources, LEDs have very long lifetimes and are generally very robust. While incandescent bulbs may have an expected lifetime (to failure) of 1000 hours, LEDs are often quoted of having a lifetime of up to 100,000 hours - more than 11 years. 

LEDs are high-efficiency light sources. White LEDs with efficacies of 25 lm/W and up are commercially available, exceeding the performance of incandescent and some fluorescent sources. The directional nature of light produced by LEDs allows the design of luminaires with higher overall efficiency. Moreover, LEDs are the most efficient illumination and lighting source, emitting more light per watt with an estimated energy efficiency of 80% to 90% when compared to traditional lighting and conventional light bulbs.

Low power consumption and Environmental 
The low power consumption of LEDs leads to significant energy savings that can often drive the installation of LED-based systems, for example traffic signals. National programs to develop effective solid-state lighting industries in the US and Japan have been driven by the potential energy savings associated with using LEDs. LED lights are free of toxic chemicals. Most conventional fluorescent lighting bulbs contain a multitude of materials, such as mercury, that are dangerous for the environment.

 LED lights contain no toxic materials and are 100% recyclable. 

The long lifetime of LEDs reduces the need to replace failed lamps, and this can lead to significant savings, particularly in the cost of sending out maintenance crews. This also makes LED fixtures useful for installation in relatively inaccessible locations.

Instantaneous lighting
LEDs switch on rapidly, even when cold, and this is a particular advantage for certain applications such as vehicle brake lights.