CMYK, or Cyan Magenta Yellow Black, refers to the colour of inks used in the printing process. CMYK inks combine in proportions to form solid colours; Yellow and Magenta with a bit of Black form a dark maroon, for example. Print design is all about CMYK and dpi (dots per inch). You want at least 300 dpi for a nice print quality.
Rule Number One in Print: Never Trust What You See On Screen.
What you see on paper will NOT look like what you have on screen, as your screen is calibrated to RGB (Red Green Blue) and not CMYK. Website design is all about RGB and pixels (72 ppi).
Although CMYK is most common today, another potential choice for printing is also Spot Colour. Effective business cards often use two or three spot colours, as it can be quite a bit cheaper by making use of solid coloured inks that span a wide range outside of what your standard combination is capable of. For instance, specialized spot colours like metallic and neon shades are possible.NOTE: you can use more than four spot colours, and potentially combine spot and CMYK in the same printing, but keep in mind that your final cost will quickly increase as the labour involved in producing these jobs becomes more complex.
Digital vs Offset Press
CMYK can be printed both digitally and also on an offset press. The latter is a traditional printing press that requires a printing plate to to be created for each colour of the ink that is printed. Four plates would be required to print the CMYK separations, and this is more expensive than digital due to the labour involved, but it is great for larger print runs and where high print quality is a must.
A digital press, on the other hand, is more or less a colour laser printer. It may be a little more expensive than your general office colour laser printer, but the output is about the same. Printing digitally is generally cheaper and is used for shorter print runs.
Your print design will dictate how you will print your file, either digitally or offset press, CMYK or Spot Colours, but never RGB as RGB is the standard colour mode for web design.
Resource: Thank you to Brian Szubinski from InkOnDaPaper for this helpful information. www.inkondapaper.com