This document provides an overview of systems for classifying, cataloging, and describing information resources including: - Classification systems like Dewey Decimal Classification (DDC) and Universal Decimal Classification (UDC) that organize knowledge into hierarchical categories. - Cataloging rules like Anglo-American Cataloguing Rules (AACR2) and Resource Description and Access (RDA) that determine how bibliographic information is recorded and accessed. - Thesauri and ontologies that organize terms and define relationships to facilitate information retrieval. - Machine-readable cataloging (MARC) standards that allow catalog records to be shared and searched electronically.