Pneumatic valves are devices used to control the flow of compressed air in pneumatic systems, similar to how faucets control the flow of water. They regulate the direction, pressure, and volume of air to actuate pneumatic components like cylinders, motors, and actuators. Pneumatic valves come in various types, including directional control valves, pressure control valves, flow control valves, and shut-off valves, each serving specific functions within a pneumatic system. These valves play a crucial role in managing air flow to ensure proper operation and efficiency in pneumatic machinery and equipment.