LED stands for Light-Emitting Diode.

Ok, but what does THAT mean?

What is an LED?

An L.E.D. Lamp is a type of bulb that uses “solid state lighting” instead of an electrical filament like your “normal” household light bulbs, or a Gas like in CFL lamps.

A light-emitting diode is a type of semi-conductor that emits light when an electric current is applied.