An engine is the power source of a vehicle—it converts fuel into mechanical energy that moves the car. It's often called the heart of the car, since it drives all motion and powers many vehicle systems. The engine is what makes your car go. Whether it runs on gas, diesel, or electricity, it turns energy into motion and keeps you moving.
A side-angle view of the Ferrari F140B engine used in the Enzo Ferrari car. © Wikimedia.org/Yanko Malinov, CC BY-SA