The color black is a common color used in design. But like other colors, not every black color is the same, as it has different shades as well.
The most obvious black color is 100% black, or expressed in CMYK: C = 0%, M = 0%, Y = 0%, K = 100%. The printing press thus only prints 100% key (black) in these places. But paper always absorbs the ink a little, which causes the color to look dark gray. This black is best used for reading texts.
To give surfaces a richer deeper black, use one of the following shades of black:
Note: make sure that the total ink coverage does not exceed 280%. A higher percentage might cause stains. You can read more about the ink coverage here.
Another shade is the "Registration Black Color". In this black 100% of each color is used (C = 100%, M = 100%, Y = 100%, K = 100%). This is used for registration marks and cut lines because they occur on every color layer. You should not use this in your layout.