CMYK

CMYK is a scheme for combining primary(RGB) pigments.
CMYK refers C- Cyan(aqua) M-Magenta(pink) Y- Yellow  K-Key (Black). 

The CMYK mode should be used when creating illustrations for print media.

About CMYK

• CMYK is composed of four colors. CMYK refers to a specific printing process.
• The black ink is not a combination of the three other colors.
• The CMYK pigment model works like an "upside-down"version of the RGB (red, green, and blue) color model.

Halftoning 

• Halftoning gives us color options. CMYK printing uses halftoning, also known as "screening".
• Halftoning allows us to choose from a wide range of printer ink colors.
• Very tiny dots of each of the primary colors are printed to produce a small pattern that humans make out as a solid color.

Differences between Halftone and original

Example