Information retrieval (IR) is the field of computer science that deals with the processing of documents containing free text, so that they can be rapidly retrieved based on keywords specified in a user's query. IR was born in the 1950s out of necessity to find useful information from large collections. Over the last sixty years, the field has matured considerably. IR technology is the basis of Web-based search engines, and plays a vital role in research, because it is the foundation of software that supports literature search. Several IR systems are used on an everyday basis by a wide variety of users. This article is a brief overview of Information Retrieval.