Color temperature is measured in Kelvin. Counterintuitively, "warm" light (candles, sunset) has low color temperature (~2700K), while "cool" light (overcast sky) has high color temperature (~7000K).
The Kelvin scale runs backward from intuition because the underlying physics refers to the color a black body radiator emits at that temperature. A cooler star is redder; a hotter star is bluer.
For shooting: tungsten (3200K) renders daylight as blue. Fluorescent (4000K) renders tungsten as orange. White balance corrects for the light source; the choice of whether to correct is aesthetic.