What is the difference between pedal-assist and throttle on an eBike?

Pedal-assist (PAS) engages the motor only when you're pedaling, providing boost proportional to your effort (torque sensor) or a fixed level when cadence is detected (cadence sensor). Throttle provides motor power on demand without pedaling — like a moped. Class 1 bikes have PAS only; Class 2 and some Class 3 bikes also have throttle. Throttle is useful for starting from a stop on hills.