All art papers have a "coating" of a fine clay-like substance that allows the ink to sit on the surface of the sheet giving a crisper edge to the image, unlike an "uncoated" paper (such as photocopy paper) or board that allows the ink to penetrate or seep into the surface.

This is not really an issue in itself, however, ink tends to dry faster on gloss art paper and generally there is no need for a coating of "trapping" varnish whereas matt art almost always requires the protection of a coat of varnish over the printed job to prevent "scuffing" or marking of the ink.