The CMYK colour model (process colour, four colour) is a subtractive colour model used in colour printing and it can be used also to describe the printing process itself. CMYK refers to the actual four inks used in the printing process: cyan, magenta, yellow and black. Though it varies by different printers and press operators the inks are normally applied in this order.
The CMYK model works by partially or entirely masking colours on a lighter, usually white background. The ink reduces the light that would otherwise be reflected.