A documentary is a non-fiction motion picture that depicts for example: A nation’s people, historic events or cultural life in the past. It was often made for the purpose of maintaining a historical record.
The purpose behind documentaries is to educate people on a certain topic, like how certain animals live, how people live in a certain country or how places looked before people settled there. It often includes pictures from said time period (If any are available).
Nowadays documentaries are often used in schools for the purpose of helping educating children, for it’s been proven that watching a movie helps retain more information than reading a textbook. They might be used by companies, to showcase their history and success in the world.