A primary source is an original object or document from a specific time or event under study. Primary sources include historical and legal documents, interviews, eyewitness accounts, results of experiments, survey data, observations, diaries, paintings, works of literature, ancient pieces of pottery unearthed in Iraq, and much more . In the natural and social sciences, primary sources are often empirical studies — research where an experiment was done or a direct observation was made.
A secondary source is anything that’s written about a primary source, such as an essay about a novel, a newspaper article about AIDS research, a history textbook, a movie review, or subsequent thoughts on The Gettysburg Address.
Tertiary sources use primary and secondary courses to construct a narrative and/or theory.