Definition of primary source material
Primary resources are actual artifacts that have survived from past historical events, including letters, photographs, physical objects such as cooking utensils from the days of westward expansion, or articles of clothing. They provide firsthand evidence of historical events, and can represent a wide variety of formats that are generally not formally published (maps, audio/video recordings, posters, postcards, government documents, diaries, court records, census bureau data that is tabulated but not interpreted, etc.). Published materials can also be viewed as primary resource materials if they come from the period that is being discussed, and were written by somebody with firsthand experience of the event. Primary resources reflect the individual viewpoint of the participant or observer. For example, newspaper articles written by somebody who experienced the event are primary sources for political science, while a literary work is a primary source for literary criticism.
Textbooks, reviews of literature published in journals, etc. are secondary source materials in that they synthesize and typically attempt to interpret the past using available primary source materials. A secondary source might include some primary source material, such as quotes from people, photographs of an event, etc.
Note: Since the definitions of primary and secondary sources may vary according to academic discipline, you may want to ask your instructor for clarification if you are working on an assignment that requires you to use primary sources. Also keep in mind that the above definitions generally pertain to the Humanities and Social Sciences, which include such fields as English, History, Sociology, Education, and the Philosophy of Science. Very different definitions apply to the hard sciences, such as Chemistry, Biology, and Physics.