CMYK

CMYK

-Cyan, Magenta, Yellow, Key

Often referred to as process or four colour, it is the method for colour printing and is known as a subtractive colour model with RGB being an additive model. CMYK is called a subtractive colour as it explains the mixing of inks creating a full range of colours, these colours caused by the subtraction of light wavelengths and the reflection of others. Subtractive models as a whole start with white light, the CMYK model in the context of printing starts with white paper (the whole, unable to print white). Out of the colour modes, the CMYK mode has the smallest colour gamete.  

Halftoning 

Halftoning is the process within CMYK printing, where tiny dots of each colour is printed in a pattern, which to the human eye look as though it is all one colour. This enables the possibility of printing a full range of colours.

This is the opposite process to Spot colour printing as that ink is printed fully, not in tiny dots.