CMYK stands for Cyan,
Magenta, Yellow and Black which are the four colours
that are used in full colour, offset printing. If
you look closely enough you will see that all
printed material is made up of tiny dots of these
RGB stands for Red, Green and
Blue. These are the colours that make up the images
of computer monitors and television screens. RGB
images often appear to be be more vibrant than CMYK
images, however, they cannot be printed.
Bleed is when you extend an
image or background colour over the crop marks of a
document so that when it's trimmed after being
printed, the colour or image goes right to the edge.
If you don't include bleed and the printer crops 1
mm out then you will end up with a white border
along the edges of your document.
Registration black is
made up of all 4 process colours (CMYK). All trim
and fold marks should be in registration black.
Professional layout programs like QuarkExpress and
Illustrator have Registration Black as a colour in
the default colour palette.