Primary sources provide firsthand evidence or testimony of a historical topic. They are typically original sources created at or near the time of the event being described. Primary sources are raw data for interpreting the past. Although it is not always the case, many primary sources are unpublished. Manuscripts and archives are examples of original, unpublished primary sources.
Secondary sources utilize a variety of resources to interpret or analyze an event. Often secondary sources will assess, review, or interpret primary sources or other secondary sources. They are typically written after the historical event occurred and usually take the form of published books and articles.
Tertiary sources identify, summarize, and compile a variety of secondary and primary sources, often into a reference source, digest, or guide.