What is a LED?

It's a "light emitting diode". In short it is a small tube which glows when energized. Unlike the incandescent light bulb, LED's have no filament to burn out resulting in much longer life. They also produce the same amount of light with approximately 10% of the electricity making them much less expensive to operate.

LEDs are real unsung heroes in the electronics world. They do dozens of different jobs and are found in all kinds of devices. Among other things, they form the numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light.

Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor.
For more information on how LEDs work go to www.howstuffworks.com

We do not want to discount the savings effect of conservation. Turning off unused lights is the first step. Some light however is necessary and should be achieved through the most efficient means technology affords.
The LED.