Grayscale color model refers to images produced using only shades of gray, white, and black.  

Grayscale data can include over 65,000 levels of gray, dependent on the bit-depth of the data frequently described as 8-bit or 16-bit gray.

Grayscale color can be used for either digital or print production.  In digital distribution, the grays are converted to RGB color mode; in print distribution, the grayscale data can be used with any number of inks or ink combinations to produce color images.

Alternate color models include CMYK,  RGB, and Lab.