They keep those records which have enduring value and are worthy of long-term preservation. Archival records include documents such as letters, reports, files, contracts, and other things which may not seem like documents, such as photographs, films, audio recordings, maps, and computer files. Records in any medium can be judged to be of value for long term preservation. Whereas library materials are most often published, archival materials are most often un published. Published material is often referred to a secondary cources of information, and archival documents are often reffered to as primary information.
Archivists differentiate between the significance of items, and the information they contain.
In some cases, original documents are preserved. In other cases, where it is only the information that is recorded, recent technological advances sometimes allow archives to keep information in more practical, inexpensive forms than that of the original documents. If they become damaged, lost, or misplaced, they are no longer available. There are no extra copies. Archival documents are often very fragile.