A library catalog is a collection of bibliographic records that itemize the information resources in a library — or a portion of them. Library catalogs generally provide author, title and subject listings for information resources that can stand alone, for example, a book, a periodical run, a database name, a cd-rom, etc.
Access in this case means only that the library catalog leads the information seeker to the information resource. Other tools are often needed to gain access to the internal parts of the resource. So, for example, a library catalog would enable an information seeker to gain access to a book by its author but it does not enable one to find an article within a periodical. Thus, its been said that a library catalog is more of a finding aid than a reference tool.