This document provides an introduction to indexing, covering some basic concepts. It defines key terms related to information systems, information retrieval, and indexing. These include defining an information system, information retrieval, information retrieval system, collection, document, index, index heading, index subheading, indexing, indexing system, index entry, qualifier, and scope note. It also discusses the general purposes and types of indexes, including author indexes, alphabetical subject indexes, and classified indexes. Finally, it outlines different levels of indexing from word and name indexes to book, periodical, and computer-based indexes.