Primary Source - A firsthand account or uninterpreted original document.
Examples: Letters, speeches, other original writings, photographs, film or video of the event, contemporaneous newspaper accounts, surveys, interviews, records, data, etc.
Secondary Source - An information source created after the time period or event by someone who did not experience first-hand or participate in the events or conditions described in the source.
Examples: Textbooks or any books or articles written after the event or time period
Primary Research Article - Not to be confused with a Primary Source, a primary research article contains original research conducted by the authors. The research reports on an empirical study (i.e. based on experience and observation rather than on deductive reasoning, abstract theorizing or speculation.)