In information science, library science, and information retrieval, an information need is person's gap in knowledge leading to a description of information they lack. It is closely related to relevance: if something is relevant for a person in relation to a given task, the person needs the information for that task.
Information needs are related to, but distinct from information requirements. They are studied for:
Information retrieval (IR) in computing and information science is the task of identifying and retrieving information system resources that are relevant to an information need. The information need can be specified in the form of a search query. In the case of document retrieval, queries can be based on full-text or other content-based indexing. Information retrieval is the science of searching for information in a document, searching for documents themselves, and also searching for the metadata that describes data, and for databases of texts, images or sounds. Cross-modal retrieval implies retrieval across modalities.
Automated information retrieval systems are used to reduce what has been called information overload. An IR system is a software system that provides access to books, journals and other documents; it also stores and manages those documents. Web search engines are the most visible IR applications.