Primary sources are original sources created at the time of an historical event or shortly thereafter by people who experienced it or felt its effects. These are eyewitness accounts, or at least very close. Primary sources serve as the raw materials historians use to interpret and analyze the past.
Secondary sources are written after an event has occurred, sometimes many years later. These sources summarize or analyze the information from primary sources. Secondary source examples include:
This video from the Hartness Library describes the differences between primary and secondary sources, and provides examples of each.