1) Documentaries aim to document reality by informing, investigating, educating and entertaining audiences on factual, subject-specific topics.
2) John Grierson coined the term "documentary" and defined it as the creative treatment of actuality. He was a pioneering documentary maker in Britain and Canada in the 1930s.
3) There are several styles of documentaries including fully narrated, mixed, fly on the wall, docudrama, docusoap, and self-reflective documentaries. Each style utilizes different techniques like narration, interviews, observation, and reenactments.