Archives usually consist of unpublished materials such as organizational records, letters, drafts, photographs, personal papers, photograph albums and scrapbooks. They can also include collections of ephemeral items like postcards, newspaper clippings, newsletters, posters and programs. Sometimes, archival collections include audio-visual material or digital files.
Basically, anything that was once in the possession of an individual or an organization might end up in an archive.
Examples of Types of Archival Material
A few examples of types of archival sources that you might consult: