In general, refers to catalogs of any type available on or compiled using a computer network, including catalogs for library collections, for shopping online, or for any other purpose. Specifically, refers to online catalogs for libraries, comprising references to materials held by a library or group of libraries that are available to the public. It can typically be searched in various ways, such as by keyword, author, title, subject, or call number, to find out what resources a library owns.