A document or other piece of historical evidence that is often written or created during or near the period under study. Primary sources vary according to the nature of the topic. Some examples are: letters, manuscripts, diaries, journals, newspapers, speeches, interviews, memoirs, documents from government agencies, photographs, audio and video recordings, research data, objects and artifacts.
A secondary source interprets and analyzes primary sources. It is one step removed from the subject; it is the result of someone else's contemplation and synthesis of primary sources. Examples are: journal articles, histories, criticisms, commentaries, encyclopedias, and textbooks.