From the word archive, archive means the collection of historical documents or records providing information about a place, institution, or group of people. It is a place where people can go to gather firsthand facts, data, and evidence from letters, reports, notes, memos, photographs, and other primary sources.
Therefore Archival materials are information objects that serve as evidence of past events. They record data about past occurrences and act like a "memory card" that enables its users to recall and relive them or to re-communicate information about those events at some point in the future.