What does doors at 9 pm mean? Do they close doors at that time or open them?

It's when the doors open to seat the people.

Doors open at 9 for the show you're attending buddy, it's also a bar/restaurant pretty cool place.

I second Sara's answer. That is when seating for a show begins. There is an outside bar and inside bar were you can get drinks prior to being seated

Seriously

It means they let people into the room at 9pm. They have several shows a night so times may vary.