yellow pages

 a telephone book or part of a book in which the telephone numbers and often advertisements of business enterprises are listed in numerous sections, organized by the category of the business, the categories themselves being arranged alphabetically; a classified telephone directory. So called because for many years the listing thus organized was printed on yellow paper, to distinguish it from the white pages containing the names of individuals, listed alphabetically by last name. The yellow pages are usually bound together with the white pages in the telephone book distributed by the telephone company to its subscribers. The name was adopted by companies not affiliated with the telephone company, for the classified business directories that they sell.  [PJC]