Crop Marks and Bleed
Crop marks, also termed as trim marks refer to the lines that are printed on the corners of paper or your artwork layout, so as to mark the trimming area for the printer. The space between crop marks and trim size is 3mm, which means that the printed paper with crop marks is bigger than trim size. Crop marks are used in commercial printing to create bleeds for artwork layouts that extend to the paper edge.
Bleed refers to the extended part of the image in an artwork layout that goes beyond the trim edge of a page. The bleed area has to be trimmed, and generally this area is either 3mm or 0.125”. In mass production, it gets quite difficult to print and trim exactly to the paper edge, but after trimming the bleed makes sure that the ink prints till the edge without falling short of the background color.