This document provides an overview of information retrieval (IR). It discusses how IR deals with representing, storing, organizing, and accessing information items like documents. The history of IR is summarized, noting that the term was coined in 1950 but gained popularity in 1961 with the introduction of computers for information handling. Key aspects of IR systems in libraries are outlined, including indexing documents, searching for information, and achieving a successful match between a user's request and relevant documents. The major functions and characteristics of IR systems are also summarized briefly.