Documentary films are non-fiction movies that aim to document reality for the purposes of instruction, education, or maintaining a historical record. They often explore real-life events, people, or issues, providing viewers with factual information and insights. Common styles include observational, participatory, and expository, each offering a different approach to storytelling. These films can cover a wide range of topics, from nature and science to social issues and historical events. Notable examples include March of the Penguins, which follows the life cycle of emperor penguins, and 13th, which examines the history of racial inequality in the United States.