An important and often confused distinction is that between editions of original prints, produced in the same medium as the artist worked (e.g., etching, or lithography), and reproduction prints (or paintings), which are photographic reproductions of the original work, essentially in the same category as a picture in a book or magazine, though better printed and on better paper. These may be marketed as "limited editions" with investment potential (which is rarely realized), and even signed and numbered by the artist. Some knowledge is often required to tell the difference.