DL Concierge - when do they make dining arrangements?

[JC Butterfly]

I have never stayed concierge before and I am trying to understand all of the benefits. Does the staff contact you before you actually stay on property or is it possible to contact them? Can they help make dining reservations?

LEt's say I want to make reservations at Goofy's Kitchen do I contact them ahead of time or do I just trust that once I arrive there are a certain number of reservations set aside for concierge staff?

Would that make it more likely to get seats to the Fantasmic Buffet?

Does concierge help make tour arrangements, etc too?

Any other perks of this?