This example is what I think of as “a world that has other ideas”

The DM (and players) build the world, but when they do so, the world will have elements that push for certain outcomes by themselves. The DM might choose for story A to happen, and the players might choose for story B to happen, but the elements in the world have defined motivations too, and might push for story C to happen. Often story C is the most exciting thing, because nobody is following a script.