LEDs: Although they are only gaining popularity now as a real alternative to CFLs, LED lights have actually been around for decades, it is only with a reduction in cost that people are now buying them en masse. LED stands for Light Emitting Diode. They come in all sizes big and small, and can be used in a variety of different situations. Each LED is made up of a solid material called a semiconductor. When electricity is passed through the semiconductor, the atoms inside release energy in the form of visible light, It is a simple, durable design with few drawbacks.