Adocument that gives us first hand historical information

Primary source.

A primary source is a historical source that originated at the time of the events by people directly participating in or affected by the events. In the case of researching persons in history, a primary source would be material from those persons themselves or from others in direct contact with them. Primary means first, and so these are the first sources of historical information.

Secondary sources are the history accounts or analyses written by others based on what is seen in the primary sources. Primary sources can be things like letters, official documents, diaries, interviews, contemporary newspaper accounts of events, as well as photographs (or contemporary paintings) and other artifacts from the person or event being studied.

Note that primary sources can be biased in the same way that all sources can be biased. If you were studying the Dakota Conflict, for instance, between white settlers and Native Americans, the sources stemming from the two sides of the conflict will have differing points of view.