An abstracting service is a service that provides abstracts of publications, often on a subject or group of related subjects, usually on a subscription basis. An indexing service is a service that assigns descriptors and other kinds of access points to documents. The word indexing service is today mostly used for computer programs, but may also cover services providing back-of-the-book indexes, journal indexes, and related kinds of indexes. An indexing and abstracting service is a service that provides shortening or summarizing of documents and assigning of descriptors for referencing documents.
The product is often an abstracts journal or a bibliographic index, which may be a subject bibliography or a bibliographic database.
Guidelines for indexing and abstracting, including the evaluation of such services, are given in the literature of library and information science.