Overdrive is a feature in a car that lets you make the engine go faster without using more gas. It's like adding an extra gear to the car's transmission, which makes it easier to drive faster and also helps the engine last longer because it has to work less. Think of it like a bicycle: when you pedal faster, the bike moves faster, but it doesn't make you push the pedals down harder. The same is true for a car with overdrive on - it will move faster, but you don't have to press the gas pedal as hard.