A documentary aims to truthfully document reality using evidence from subjects like politics, history and religion. While the content aims to be authentic, recreations are sometimes needed due to the unpredictable nature of capturing real events as they happen. Documentaries use conventions like narration to anchor meaning and guide the audience. There are different styles of documentaries such as observational, interviews, dramatizations, and styles that mix genres. The intended audience and what can be shown helps determine the type of documentary and advertising used.