WTF is a World Model? [D]

Excerpt

I'm trying to understand what a world model is. I understand it has its roots in cognitive science and reinforcement learning. I understand at least at the moment what most people are building which they call world models are fancy video generation models. But what actually counts. Does a simulator count as a world model. Some "world models" are described as simulators, or rather a simulator is described as one type of world model. But is a simulator like lets say a physics engine a world model?