What is the purpose of a tub overflow valve and how does it prevent water from overflowing in a bathtub?

The purpose of a tub overflow valve is to prevent water from overflowing in a bathtub. It is typically located near the top of the tub and serves as a safety feature. When the water level reaches a certain point, the overflow valve allows excess water to drain out through a separate pipe, preventing the tub from overflowing.