Check out this video from the University of Guelph libraries for a quick introduction to primary and secondary sources. Or read the definitions below.
Primary Sources
Primary sources are original records or objects that provide first hand testimony or direct evidence about an historical event or topic.
They are usually created by witnesses who experienced the events or conditions in question. Often these sources are created at the time the events occur, but primary sources can also include memoirs and oral histories recorded later.
Secondary Sources
Secondary sources describe, discuss, interpret, comment upon, analyze, evaluate, and summarize primary sources. Secondary sources are created after the event in question and often present primary source information with the addition of historical perspective.
Common examples of secondary sources include articles in newspapers or popular magazines, books and articles found in scholarly journals that discuss or evaluate someone else's original research.