What is meant by the throttle a car?

In a car, the throttle is the mechanism that controls the amount of fuel delivered to the engine. By pressing the accelerator pedal (the gas pedal), you're actually controlling the throttle. This increases or decreases the opening of a valve (or a butterfly valve in many modern cars) that regulates the airflow into the engine. More airflow means more fuel is injected (or drawn in via a carburetor in older cars), leading to a faster engine speed and increased power.