LED stands for light-emitting diode. LEDS are similar to small light bulbs. Put basically, they can light up because of electrons which move in a semiconductor material.
Less Energy Consumption – LED flashlights use a fraction of the energy incandescent flashlights consume. Incandescent lights work by heading a narrow wire inside the bulb, generating both light & heat. Regrettably, much of the energy needed to generate light is lost in the type of heat. By using LEDs, less of the energy is lost to heat, meaning the same amount of light requires less energy to produce.
The main advantage of military designed tactical flashlights is that you will get much more use out of the battery. Some flashlights can run for hundreds of hours on set of batteries. LED flashlights also tend to be more long lasting than traditional flashlights. Also, LED flashlights are made so that the light remains constant even as the battery is dying. This is an advantage over traditional flashlights which grow dimmer as the battery wears out.
Lenses of these flashlights are obtainable in a variety of materials. Some lenses are made of glass while others are of plastic. Some lenses are very complex like Lexan, which is a clear, shatterproof plastic lens. Plastic lenses are usually not used in flashlights that have very high output as these may melt due to the heat that is generated by the bulb.