Fairly often, science fiction authors are not quite aware of the proper terms to use. More than once I have read that the aliens then took the human to their own universe. I am going to assume, that the author wasn’t talking about the multiverse theory (stating that there are an infinite number of universes existing alongside each other, travel between them may or may not be possible) since that was never even alluded to and guess that they probably meant galaxy. Here is reality as we know it for sure so far: There is one universe that started with the Big Bang. It is constantly expanding. In this universe there are many galaxies, clusters of stars and other matter, interacting with each other. Our own galaxy is called the Milky Way. In each galaxy there are star systems. Planets and asteroids circle their star(s). Our star system is called the solar system (after the sun). Some of these planets may or may not contain liquid water and even fewer will contain life. So far we only know of one, Earth. The nearest star system is called Alpha Centauri and is 4.37 light years away. At current speed it would take us several millennia to get there. So you don’t need to go to a different universe to get really, really far away. Even going to a different galaxy is a concept that is so improbable as to make me wary.