There are only two worlds--your world, which is the real world, and the other worlds, the fantasy. Worlds like this are worlds fo the human imagination: their reality, or lack of reality, is not important. What is important is that they are there. These worlds provide an alternative. Provide an escape. Provide a threat. Provide a dream, and power; provide refuge, an pain. They give your world meaning. They do not exist; and thus they are all that matters.