A documentary is a movie or television program that presents real events, real people, or real information rather than telling a made-up story. When you watch a documentary about ocean life, you're seeing actual footage of dolphins, sharks, and whales swimming in their natural habitat, not actors in costumes. When you watch a documentary about Abraham Lincoln, you're learning true facts about his life through historical photographs, expert interviews, and dramatic re-creations of actual events.

Documentaries aim to inform, educate, or reveal truths about the world. They might explore how chocolate is made, follow scientists studying volcanoes, or tell the story of an athlete overcoming obstacles. Unlike fictional movies where writers invent everything, documentary filmmakers research their subjects carefully, interview real people, and gather actual footage or evidence.

Some documentaries show nature and wildlife, others investigate historical mysteries, and still others follow real people through important moments in their lives. The filmmaker's job is to capture truth and present it in a way that helps viewers understand something real about the world.