What do "cool white" and "warm white" mean, and what is CCT?

The Color Correlated Temperature (CCT) is given in the description of each of our white led bulbs. The color (CCT) of our white bulbs ranges from a warm yellow white (2700K) to a cool blue white (7000K). By comparison, a typical incandescent bulb has a CCT of 2800K. A typical halogen is a bit higher, maybe 3500K. Daylight white is 4500K and a cool white fluorescent is 6000K or more.
 

The human eye adapts to background light so that even a daylight white bulb will look slightly blue in a room illuminated mainly with incandescent bulbs. Similarly, an incandescent bulb will look very yellow or even orange in midday sunlight.