Can someone give me a much simplified explanation?

Question

Of L.E.D. light emitting diodes? I understand filaments and arc lights fairly well but light emiting diodes are beyond my understanding.

Answer 1

I doubt there is a simple explanation of solid state physics. Once it was discovered that charge carriers crossing the energy band gap in a diode released energy in the form of a photon, people began to engineer the devices to maximize this light output, rather than other useful diode properties.

Answer 2

I don't know your background. But hope you know what diodes are. If you know that please go to the following link
for a good explanation.
http://electronics.howstuffworks.com/led2.htm