Pedal Assist automatically turns on the motor when you pedal. With pedal assist, you do not need to use a throttle to control the motor.
There are two types of Pedal Assist: Cadence Sensor Type, which measures IF you are pedaling and a Torque Sensor Type, which measures HOW HARD you are pedaling. The Super73 S-Series sold in the United States with thumb throttles, as well as the Super73-SG (Global), has a cadence sensor. The Super73-SG1, sold outside North America without a throttle, has a torque sensor.