While a directory can often in itself be a source of interesting genealogical and biographical information, its chief value lies in its use as an aid to locating a person in place and time. One type of directory groups people by a common residence. The second groups them by a common association or attribute. In addition, many directories cover organizations rather than individuals and are sometimes called registers, catalogs, annuals, yearbooks, or guides. Whatever its title, contents, or method, a directory will always list and locate members of a group.