Primary sources are the evidence of history, original records or objects created by participants or observers at the time historical events occurred or even well after events, as in memoirs and oral histories. (Taken from RUSA)
Primary sources may include but are not limited to:
Primary sources are the raw materials of history — original documents and objects that were created at the time under study. They are different from secondary sources, accounts that retell, analyze, or interpret events, usually at a distance of time or place. (Taken From Library of Congress)
In Summary; Primary vs Secondary resources:
Ex. audio recording of an interview with Dr. King (primary source) vs article with a quote from the audio recorded interview with Dr. King (secondary source)