There are so many different worlds within this one world, this 'real' world, we ALL share and call home.
There's my world, for one. And your world, for two. And you or I can both know the experience of Billy over there and visit his world through empathy, for three.
And we can go online and have the opportunity to visit millions of different worlds, each different from the next.
We can open a book and visit the world an author is creating with us, and we can turn on our screen and watch different world's others have created for us.