CMYK is also called 4-color process. Colors in CMYK images are composed of varying amounts of Cyan, Magenta, Yellow, and Black. This is the way a printing press prints color, so it is vital that your image be in this color mode. For 1-color process it needs to be grayscale or bitmap (which only uses Black).
Refers to a method of specifying and printing colors in which each color is printed with its own ink. In contrast, process color printing uses four inks (cyan, magenta, yellow, and black) to produce all other colors. Spot color printing is effective when the printed matter contains only one to three different colors, but it becomes prohibitively expensive for more colors. Most desktop publishing and graphics applications allow you to specify spot colors for text and other elements. There are a number of color specification systems for specifying spot colors, but Pantone is the most widely used.
Pantone Matching System (PMS):
A popular color matching system used by the printing industry to print spot colors. Most applications that support color printing allow you to specify colors by indicating the Pantone name or number. This assures that you get the right color when the file is printed, even though the color may not look right when displayed on your monitor. PMS works well for spot colors but not for process colors, which are generally specified using the CMYK color model.