What defines an "e-bike" varies from jurisdiction to jurisdiction. It also changes when talking in a colloquial context.

There are electric riding devices that are bicycle-shaped that go up to 45 mph (72 km/h) that are being sold as "e-bikes".

It's why it's hard to talk about e-bikes and regulation surrounding them because you can say "e-bike" and people think you're talking about entirely different things.

For example, in Oregon, for something to be an e-bike, it must be only pedal-assist and only up to 250 watts, which really will only take you to about 15-20 mph. If it has a throttle button so it doesn't require pedaling, then it's classified as an e-motorcycle, regardless of power rating, and so is licensed and registered like a motorcycle.

But enforcement is weak, and parents often don't know, so they'll buy their kids what is legally an e-motorcycle and they'll rip through neighborhoods at 45 mph, not even aware that their kids even riding one at all is illegal.