The printing process uses the CMYK system consistent of four basic colors, CYAN, MAGENTA, YELLOW and BLACK to make all the colors. Creating your documents using this COLOR MODE will allow you to better match the colors on your screen to the colors on the printed material.
Originally created for Television, the RGB system uses three light sources, RED, GREEN and BLUE to reproduce all the colors on the spectrum, This color mode produces more vivid colors on the screen but not all of them can be accurately reproduced on print.
BLACK vs RICH BLACK vs REGISTRATION BLACK:
For deep real blacks choose Rich Blacks (C: 30, M: 30, Y: 30, K: 100) instead of Just Black (C: 0, M: 0, Y: 0, K: 100). Do not use Registration Black (C: 100, M: 100, Y: 100, K: 100) because it may smudge.