Raised print raises up from the surface and can be felt to raise up from the paper when touched. Raised print cannot go through laser printers.
Letterpress digs in to the paper service, and the indent can be felt within the paper when touched. To get the best letterpress effect we recommend you use impression board as this allows the letterpress printing to dig in very well to the surface of the paper.
Copperplate and die-stamped require dies or plates to be engraved and also create a raised effect.
Flat is just normal print and cannot be felt when touched.