The color of light, expressed in Kelvins (K). The sun is about 5800 Kelvins. This is called a "temperature," because the hotter fire gets, the more it changes from a warm yellow glow to white.
The higher the kelvin rating, the colder the color temperature. Bright or cool white light ranges from 7,000K to 10,000K. This light is great in dimly lit spaces like garages, attics, and work sheds.