Discussing the concept of indexing and index term weighting in information retrieval. Indexing involves mapping documents with keywords, termed index terms, to describe documents and queries in an information retrieval system. Two methods are pre-coordinate (indexing before search) and post-coordinate (indexing with term weighting before search). Controlled vocabulary assigns predefined keywords as index terms, while uncontrolled vocabulary determines index terms during processing. Index term weighting aims to enhance the effectiveness of the information retrieval system by focusing on relevance and precision of results. Effectiveness in information retrieval is measured by the relevance of listed documents to queries, emphasizing precision in search results.