A control valve is a valve that regulates fluid flow by changing the size of the flow passage in response to a controller signal. This allows for direct flow rate control as well as control of process variables including pressure, temperature, and liquid level.
A pressure regulator is a control valve that lowers a fluid's input pressure to a desired output pressure. Regulators are used to control the flow of gases and liquids. They can be integrated devices that include an output pressure setting, a restrictor, and a sensor, or they can be separate devices that include a pressure sensor, controller, and flow valve.