Letterpress; debossing; embossing

Three processes people lump together because they all deform the sheet. Letterpress inks a raised plate and presses it in, leaving color plus a dent (the 'bite'). Debossing presses a die down so the shape sits in a clean recess, and that recess can be blind, inked, or foiled in the same hit. Embossing uses a matched male and female die to push the shape up from behind. Blind just means no ink and no foil, so blind deboss and blind emboss are both normal orders.

All three like soft, thick, uncoated stock, because a bulky compressible sheet holds a deeper impression: cotton and heavy uncoated papers, often two sheets duplexed. None of that is a hard requirement though. Lighter and coated sheets take a shallower impression fine, they just bruise, crack, or lose definition sooner. Reach for them on identity pieces, invitations, wine labels, and book covers, where the point is that someone runs a thumb over it. Budget for a die or plate charge per design and a slower press run.

Gotchas: the impression shows on the reverse (printers call it bruising), so heavy work on both sides of one sheet fights itself. Letterpress hates large solid ink areas, which come out mottled: it wants line art and type. Fine type below roughly 6pt fills in on letterpress and vanishes when debossed, and coated stock cracks its surface when embossed hard.