LED is an acronym for Light Emitting Diode.. the link is to an article that describes a light emitting diode in layperson terms. An LED can produce more light (measured in lumens) with less energy (measured in watts) than a traditional incandescent bulb.

A diode that emits light when electricity is passed through it. Diodes are single directional devices, which means they prevent electricity from reversing or flowing backwards and so, are relatively safe to use and potentially can prevent damage to other connected devices if a high voltage fluctuation happens. They also are energy efficient, resulting in smaller electricity bills.