Wes,
if you want to know how all combinations of CMYK values look on YOUR printer, then you may print the first pages of this swatch book:
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http://www.fho-emden.de/~hoffmann/swatch22112002.pdf>
A typical application is the design of posters which are definitely intended for printing by a specified inkjet. Essential are the CMYK numbers. A preview on the monitor is possible if the printer has an ICC profile.
Best regards –Gernot Hoffmann