CCT means you can control your colour temperature:
https://en.wikipedia.org/wiki/Color_temperature
For painting purposes, it practically means that you can control if the lamp emits 'clinical' cold white light, 'natural' feeling quasi-daylight or some 'softer' lighting that might match what you have in mind for a presentation cabinet or diorama.
In layman's terms, it means you can make your lamp-light have a tint ranging from light-blueish to light yellow-reddish.
It's mostly useful if you want to paint exhibition or competition pieces or want to do professional photography of your painted models, as it allows you to simulate the effect of harshcabinet lighting or camera flash a bit better than other lamps, and prevents your miniatures from looking starkly different at your painting desk and in the cabinets/softboxes.