A throttle valve is a device used to control the flow of air or fuel into an engine, particularly in internal combustion engines. It regulates the amount of air entering the engine, which in turn affects the engine's power output and efficiency. The position of the throttle valve is typically controlled by the accelerator pedal in a vehicle. In modern vehicles, throttle valves are often electronically controlled, allowing for more precise adjustments. This system is known as drive-by-wire, where sensors detect the driver's input and send signals to the throttle valve, improving responsiveness and fuel efficiency while reducing emissions.