Archives or archival collections usually have unique materials generated or collected by a person or organization in their work or activities. The word "archive" may refer to a building or institution that holds these materials, or it may refer to the materials themselves. In either case, archives are often excellent sources of primary sources.
Most archives collect materials related to a certain region, topic, historical period, or institution. A university may have an archive of records documenting the activities of the university and its students, a city may hold materials related to its own history and government, or an art museum may collect documents related to artists and a particular type of art.
Because most archival collections contain a group of unique materials, descriptions of archival collections are created.