what is the actual name for the type of seat commonly found in art galleries? it is more like a low rectangular cushioned table than a traditional seat, because it has no back. usually they are in the middle of a hallway in an art gallery, so people on both sides of the hallway can sit on it, facing their wall.

what is it called?

A piece of minimalist art.

Jokingly apart, I once heard of someone who was deeply interested in an item while visiting a modern art gallery, until someone politely explained to him that this item was an authentic fire-extinguisher and not at all a piece in display.

I don't know whether it's true or not, but it is likely, I believe.