Catalogues register the book and journal holdings of one or several libraries. They make it possible to research locations and shelf marks in order to gain access to specific media. Catalogues usually do not register articles in journals and contributions in collections.
Databases usually record literature belonging to a specific subject. It is possible here to search thematically for articles in e-journals or contributions in collective works. The thematic search is followed (often automatically) by a catalogue search for the locations of the found books and journals.