Documentary
A nonfiction film. Documentaries are usually shot on location, use actual persons rather than actors, and focus thematically on historical, scientific, social, or environmental subjects. Their principle purpose is to enlighten, inform, educate, persuade, and provide insight into the world in which we live.
Get two documentarians together, and the chances are high that they will argue about what a documentary is. Even though documentary has evolved continuously from its inception, its purview and methods remain ambiguous, and its parameters keep enlarging. Uncontested, however, is what remains central to documentary’s spirit, the notion that documentaries explore the mysteries of actual people in actual situations. Successful documentaries, like their fiction counterparts, tell a good story and have engaging characters, narrative tension, and an integrated point of view.
SOURCES:
http://www.realityfilm.com/study/definitions.php
Michael Rabiger. Directing the Documentary. 4th Edition. 2004. p. 4