A ball valve is a type of quarter-turn valve used to control the flow of fluids in a variety of applications. It consists of a spherical ball with a hole in the middle that allows fluid to pass through when the valve is open. The ball is held in place by a stem that can be rotated by a handle or actuator, which controls the position of the ball and thus the flow of fluid through the valve. Ball valves are commonly used in applications where high flow rates and low pressure drops are required, such as in water and gas pipelines, and are known for their reliability, durability, and ease of operation. They are also available in a variety of materials, including brass, stainless steel, carbon steel, and PVC, to suit different applications and environments.