I have a DAS-Kit 500 watt rear hub drive with 6 PAS settings. It only detects that you are turning the pedals. Each settings 1-6 will propel you to a certain speed if the pedals are turning. For example 1 = 10mph, 2 = 12, 3 = 14, etc.... If you are riding with a group going 13mph, then you could put it on 2 and pedal a little harder. Or you could put it on 3 and pedal intermittently so that it stays around 13mph. Basically the PAS setting sets your target speed. A setting of 6 doesn't produce any more acceleration than a setting of 1. It also includes a throttle so that no pedaling is required.

I also have a mid drive mountain bike with a Bosch motor. It doesn't have any settings that work like the PAS above. It uses torque and cadence in different ways depending the assist setting.