Semaphore is a system used for sending messages over long distances using visual signals. It typically involves two flags held in specific positions to represent different letters or numbers. This method was commonly used before the advent of modern communication technologies, allowing people to communicate quickly across vast areas, such as on ships or between military units. The concept of Semaphore can also be found in computer science, where it refers to a synchronization tool used in programming. In this context, it helps manage access to shared resources, ensuring that multiple processes can operate smoothly without interfering with each other.