Kahn's Theorem is a fundamental result in graph theory that deals with directed acyclic graphs (DAGs). It states that for any finite DAG, there exists a way to order the vertices such that for every directed edge from vertex A to vertex B, A appears before B in the ordering. This property is essential for tasks like scheduling and organizing dependencies. The theorem is named after Robert Kahn, who contributed significantly to the field of computer science. Kahn's Theorem provides a systematic approach to understanding the relationships between tasks or events, ensuring that prerequisites are addressed before subsequent actions are taken.