Kelvin is a unit of measurement for the colour spectrum. Lower numbers on the scale correspond to colder colours such as blues and purples, while higher numbers indicate warmer colours such as reds and yellows.
Kelvin is often used to measure the colour temperature of light sources, such as lamps and LEDs. The colour temperature of a light source can be affected by its type, how it is made, and the surrounding environment. For example, incandescent bulbs tend to have a lower colour temperature than fluorescent bulbs. Light sources with a high colour temperature are said to be “cool” (5000K), while those with a low colour temperature are “warm.” (3000K)