Primary sources are original sources that have not been interpreted, discussed or analyzed. They can include first-person accounts of events, interviews, data obtained through original research, statistics, novels, artifacts, or historical documents. Types of sources falling into this category vary by discipline. However, some differentiate between the raw data and the analysis. For example, if a political scientist wrote an article discussing the results of a survey she conducted, the survey data could be considered primary and the researcher's conclusions secondary.
Secondary sources restate, explain, analyze, interpret or discuss primary sources.
Examples of tertiary sources are encyclopedia articles and textbooks, which summarize knowledge on a given topic.