Primary sources provide first-hand testimony or direct evidence concerning a topic under investigation. They are created by witnesses or recorders who experienced the events or conditions being documented. Often these sources are created at the time when the events or conditions are occurring, but primary sources can also include autobiographies, memoirs, and oral histories recorded later. Primary sources are characterized by their content, regardless of whether they are available in original format, in microfilm/microfiche, in digital format, or in published format.
Yale University, What is a Primary Source
http://www.yale.edu/collections_collaborative/primarysources/primarysources.html
Primary sources enable you to get as close as possible to understanding the lived experiences of others and discovering what actually happened during an event.
Reviewing primary source material can be of value in improving your overall research paper because they:
Examples of primary documents you could review as part of your overall study include: