What are RGB/CMYK/HSI color models?

here is a very simple & scientific document about the 3 models http://www.cs.uleth.ca/~cheng/courses/cs4850/slides/colour-4up.pdf

RGB: Computer creates the colors based on RGB model.
It produces spectrum of visible light.
Monitor can create millions of colors by combining different percentages of three primaries, red, green and blue.
CMYK: Printing inks are based on this model.
With the full presence of cyan, magenta and yellow we get black.
HSV (HSI): Often used by artists because it is often more natural to think about a color in terms of hue and saturation than in terms of additive or subtractive color components.
HSV is a transformation of an RGB colorspace, and its components and colorimetry are relative to the RGB colorspace from which it was derived.