i think you mean planes of existence. we are the physical plane, there's the ethral and the astral. [those are the ones i know of anyway] the ethral is sort of like the spirit world, when you first project out of your body, you would be in the ethral plane. [basically the physical but you'd be able to move around the world seen by few people] then you think of the astral and you should instantly show up there. people are divided on the astral plane, as some feel it's a land of fantasy since its inhabitant are a lot of fictional creatures such as mermaids and vampires.
i have also heard of people creating their own realms but i've never looked into it as it doesn't interest me, so i don't know about that.