Link: http://www.bcnorthernlights.com
This is kind of geeky, but also kind of cool...What is an LED? A light-emitting diode (LED) is an electronic light source introduced as a practical electronic component in 1962. The first LEDs were mostly used in expensive equipment such as laboratory and electronics test equipment, then later in TVs, radios, telephones, calculators, and even watches.
Follow up:
Now, LED's have all forms of practical usage, not the least of which is indoor gardening. LED grow lights are used as a in the most popular form of indoor gardening, hydroponics. When plants are grown outdoors, they need the nutrient providing sunlight to provide them with a full light spectrum range. But, sunlight is not plentiful enough indoors so it must be augmented so hydroponic lights are used to imitate what the sun's light spectrum can do for plants. If you refresh your knowledge of physics and chemistry, you’d know that sunlight is produced when photons, contained by the atoms, move around or change electron positions. This continuous process produces sunlight. LED grow lights work with the help of electricity, re-producing this process.
Now, while the sun itself produces light in all spectrum's, here are certain spectrum's that a plant cannot use, such as the green light spectrum, so artificial indoor light with that spectrum are wasted on plants. With hydroponic lights, though, this is not always the case. Many indoor grow lights are designed with one particular spectrum, usually either red or blue, while others are full-spectrum grow lamps appropriate for all stages of plant growth.
What this means is that if you are growing seedlings on to maturity, you may need to have different hydroponic lights on hand in order to give them the appropriate light spectrum they need when they need it. Be conscious of what you are growing and what light spectrum your plant requires prior to purchasing an LED grow light.