A good glossary of German archival terms is found here:
Glossar (Uni Hannover)
Jürgen Seefeldt und Ludger Syré
Portale zu Vergangenheit und Zukunft - Bibliotheken in Deutschland. Im Auftrag von Bibliothek und Information Deutschland e.V. (BID) herausgegeben. Mit einem vorwort von Claudia Lux. 4. überarb. Aufl. Hildesheim: Olms Verlag, 2011.
An organized collection of the noncurrent records of the activities of a business, government, organization, institution, or other corporate body, or the personal papers of one or more individuals, families, or groups, retained permanently (or for a designated or indeterminate period of time) by their originator or a successor for their permanent historical, informational, evidential, legal, administrative, or monetary value, usually in a repository managed and maintained by a trained archivist (see this example). Also refers to the office or organization responsible for appraising, selecting, preserving, and providing accessto archival materials.
Archives can be classified in three broad categories:
The term is also used in academia to refer to a repository of electronic preprints, working papers, and similar documents, commonly called e-print archives. Used in this sense, there is no implication of archival management, which has caused some confusion, for example, around the purpose of the Open Archives Initiative (OAI).
From: Joan M. Reitz. ODLIS Online Dictionary for Library and Information Science. http://www.abc-clio.com/ODLIS/odlis_A.aspx
"In scholarship, a document or record containing firsthand information or original data on a topic, used in preparing a derivative work. Primary sources include original manuscripts, periodical articles reporting original research or thought, diaries, memoirs, letters, journals, photographs, drawings, posters, film footage, sheet music, songs, interviews, government documents, public records, eyewitness accounts, newspaper clippings, etc." (ODLIS). In literary research the author's works are considered a primary source.
Obviously primary sources are held in all kinds of institutions, not just archives, and may be in the format of microfilm, facsimile reproduction, free online and subscription databases, reprinted in books, etc. Check out the catalog tips for finding primary sources.
Depending on the type and the relative importance of material and size of a collection or archive, searching for an archive might involve finding any of the following types of information:
Clio Guide to Archives Sebstian Barteleit
Using Archives (Practical Advice from Canadian Library Association)
Using Manuscripts and archives: a tutorial (Yale University)
Archival records use a specialized language to describe items in the catalog or in a finding aid. Use this glossary to understand the record:
A Glossary of Archival and Records Terminology