Coated paper
Also called Gloss, silk, matt coated
Paper with a thin mineral coating that seals its surface, so the ink sits on top instead of soaking in: sharp dots, dense colour. It comes as gloss, silk and matt.
In practice
It is the paper for illustrated books. In gloss it is a poor one for long reading, since it throws back the light of a reading lamp. At the same gsm it is thinner than uncoated stock, and at the same thickness heavier, which changes both the spine width and the postage. Ask for a blank dummy in the actual paper before you accept the quote.