The colour temperature (unit Kelvin K) specifies the colour of the light. The higher the value, the "colder" the effect of the light. Under 3,300 K the light is designated as warm white, between 3,300 K and 5,300 K neutral white and from 5,300 K cool white light is emitted.

See also:

Light colour
Lighting mood
Kelvin
Warm White
Cold White
Neutral-white