CMYK stands for Cyan, Magenta, Yellow, and Key (the printer’s term for Black). These are the colors that are traditionally used by an ink printer to produce printed paper materials.
When setting a CMYK color, the numbers range from 0 to 100 which is actually the percentage of the ink required to make that color. For example, pure black is C0, M0, Y0, K100.
When you print your design, we will convert your file to CMYK, but it is really important to realize the printed result may be very different from what you see on your screen. One is made with light (RGB) and one is made with physical ink. Bright colors like orange and bright green will appear much duller on the printed paper. Just something to bear in mind.