Trim Marks are small lines showing exactly where the finished page will be cut during the finishing process
Registration marks are a little circle with a cross through it printed with every colour CMYK. If everything is aligned, it will show black. If one is off, it will be off
A colour bar is squares of colour printed on an area to be trimmed away
Colour Bars are used to check colour density and consistency
Colour Bars can be done manually or using a densitometer (a hand held scanner)