Most e-bikes are "assisted" rather than having a motorcycle-style twist throttle. You pedal and the motor contributes some additional power until you reach a certain speed (typically 20mph in the US, 25kph in Europe). At this point the motor stops assisting and the rider is contributing 100% of the effort. If you stop pedalling the motor stops assisting, regardless of your speed.
In other words the motor will help you accelerate to 20mph but beyond that it's just your legs pushing a heavy bike.
In other words the motor will help you accelerate to 20mph but beyond that it's just your legs pushing a heavy bike.