Authority control is a way of associating a unique identifier to articles on Wikipedia. This is useful to disambiguate different items with similar or identical headings, as well as to establish a single standard title for an item that is commonly known by two or more titles. When used, authority control data links can be found near the bottom of Wikipedia pages, linking to bibliographical records on worldwide Library catalogs. Authority control is often used on biographical articles because it is quite common for more than one person to share the same name. It is commonly used in other subject material, as well.
Authority control enables researchers to search more easily for pertinent information on the subject of an article, without needing to disambiguate the subject manually.
More generally, authority control is a method of creating and maintaining index terms for bibliographical material in a library catalogue. The links produced by the authority control template on Wikipedia go to authority control data in worldwide library catalogues. As an example, the Wikipedia authority control information for Alexander Graham Bell looks like this:
WorldCat is a global cooperative union catalog which itemizes the collections of 72,000 libraries in 170 countries and territories. What follows are four authority control records: Virtual International Authority File (VIAF), the second is the Library of Congress Control Number (LCCN), then the International Standard Name Identifier (ISNI), and last the GND is the Integrated Authority File (in German).