A signal flag is a type of flag used to convey information, especially in maritime communication. These flags are often brightly colored and have specific patterns that represent different letters, numbers, or messages. Ships use signal flags to communicate with each other over long distances, especially when radio communication is not possible. The system of signal flags is known as the International Code of Signals. Each flag corresponds to a letter of the alphabet or a specific message, allowing vessels to share important information such as their intentions or requests for assistance. This method of communication has been essential for safe navigation at sea.