Paper folds smoothly with the grain and is stiffer. When folded across the grain, it can crack or become rough. For example, grain direction in books and catalogs should be parallel with the binding edge to reduce curl and make the pages lie flat and turn easier. Basis Weight is a way of identifying paper. The basis size in the U.S. is not the same for all grades of paper - book paper, cover paper, bond paper, newsprint, etc.
Color affects the color reproduction of lighter tints.
Paper colors vary with advertising fads from cool to warm shades. Type is more easily read against a soft or yellowish white, while process colors reproduce most accurately on neutral white paper. Gloss affects the appearance of the ink film. Smoothness is a very important property for letterpress and gravure, but has little effect on offset. Smooth surfaces have irregularities that cannot be seen by the naked eye, but can be detected by a magnifying glass.