To answer the question "what waves a flag," it is important to understand that a flag is a piece of cloth that can be attached to a pole and used as a sign, signal, or symbol of something, especially of a particular country. Therefore, a flag does not wave on its own, but it is waved by external factors such as wind or a person. When a flag is attached to a pole, it can be waved by a person holding the pole and moving it back and forth. Alternatively, when a flag is not attached to a pole, it can be waved by the wind. The movement of the flag caused by the wind is known as a wave, which is why some flags have designs that include waves. In summary, a flag is waved by external factors such as wind or a person holding the pole.