What exactly does a government shutdown mean? I've seen shutdowns before, and nothing seems to happen.

I know government employees might not get paid. Beyond that... 🤷‍♀️

And if it was shutdown, as I understand the word shutdown (off, disabled, not running), how would if ever start back up? Don't they need to vote on whatever it was that lead to it shutting down? It's shutdown, so who's there voting?