To the best of my recollection, there are three separate levels of “no”:
1) No parking – the least severe.
2) No standing – you can drop off or pick up a passenger, but you can’t remain in the spot, even if you stay in the driver’s seat with the engine running. A bus stop is an example.
3) No stopping – you can’t even stop to let someone out. If you can’t pull over to the curb and you pull over next to a parked car to let someone out, you are in violation. This is usually not enforced for drop-offs and pick-ups, but occasionally people get ticketed for this. If you double-park you are in violation of the no-stopping area and can be ticketed. Remaining in the drivers seat (even with the engine running and the car in gear) makes no difference.