Even more confusingly, "moped" often means a less powerful "scooter". In Czech, "moped" is 50ccm, scooter ("skůtr", pronounced the same) is up to 125ccm.
It means both, youngin’, and has as long as I remember. There was a change to the API these last few years where calling the scooter() method with no parameters now gives you a kick scooter, but you can still call using the withSeat flag and get a step-through vehicle.
Mopeds have a specific definition and history involving pedals--a scooter is more commonly used to refer to a gas powered, step-through motorized cycle.
Not in the regions of the US where I’ve lived. Here mopeds are step through 2 stroke gasoline motorcycles, while scooters are foot or electric powered vehicles you stand on.
(Confusingly, mopeds are often called scooters in non-English speaking countries.)