Light is made up of particles of energy called photons, which create waves or wavelengths of energy. How intense the light is in your aquarium depends on the lux ratio, a measurement of light from its source to the bottom of your tank.
There are basically two types of aquarium lighting — fluorescent and incandescent.
Fluorescent lights involve the transmission of rays of mercury vapor. These cause the inside of a chemically-coated light bulb to glow. Fluorescent lighting is praised in aquariums for several reasons: