The distinction is web workers and offline mode.
It means your PWA can preload everything it needs to run offline, and you can actually use it offline. That is different from a "cached website" which can only cache the pages you've already visited and otherwise does not allow you to update data locally.
You mean pretty much a single GitHub account?
Also your quick question may have already been asked and answered but difficult to find on Discord. Or if it hasn't been asked yet, now a future person can't discover the same question easily. So either way you're just wasting other people's time.