A tree diagram is a visual representation used to illustrate the relationships between different elements in a structured way. It resembles a tree, with a main trunk representing a primary concept and branches that extend to show subcategories or related ideas. Tree diagrams are commonly used in fields like mathematics, computer science, and linguistics to organize information clearly. These diagrams help in breaking down complex information into simpler parts, making it easier to understand and analyze. They can also be used to display decision-making processes, where each branch represents a possible outcome or choice. Overall, tree diagrams are effective tools for visual learning and organization.