Primary Source: First Hand, from the time the event took place
Eg. Notes, Letters, Photos, Interviews, Newspapers, Art, Film
Secondary Source: Second Hand, an analysis of events
Eg. Books, Editorials or Analysis in Newspapers, Web pages, Biographies, Dissertations, Documentary Films.
In cultural studies secondary sources are published materials such as books, journals and newspapers, press releases, and authoritative web sites. Secondary sources are generally collected by libraries and are inventoried in catalogs such as the Library Catalog. Catalog content may be limited to simple citations (directing you a physical object such as a book) or it may be fully integrated with digital content such as databases or full-text journals.
Primary sources are artworks and unpublished materials such as letters and memos, draft documents, internal reports, technical drawings, and other forms of direct documentation (moving images, sound recordings, transcripts, photographs). Primary source materials are generally collected by archives and inventoried in finding aids.
To discover archival collections, consult ArchiveGrid, a database of primary-source collection finding aids. Archival collections and finding aids are also readily discoverable through Google searches.
Source: MoMA Library