It's general admission, so if you have a ticket you'll get in, but making a reservation guarantees you a table, and sometimes you can request how close/far away you sit. If you don't make a reservation, you can sit at any tables that might be left, sit at the bar, or stand. It's a very small venue, so you can see perfectly from just about anywhere you end up, but if you want a table, your best bet is to make a reservation. I think the food/drink minimum is higher if you make a reservation, but when I was there, they were really flexible and didn't hold to it at all.
A work of art is an invitation to love.