[Gaal] had steeled himself just a little for the Jump through hyperspace, a phenomenon one did not experience in simple interplanetary trips. The Jump remained, and would probably remain forever, the only practical method of traveling between the stars. Travel through ordinary space could proceed at no rate more rapid than that of ordinary light (a bit of scientific knowledge that belonged among the items known since the forgotten dawn of human history), and that would have meant years of travel between even the nearest inhabited systems. Through hyperspace, that unimaginable region that was neither space nor time, matter nor energy, something nor nothing, one could traverse the length of the Galaxy in the interval between two neighboring instants of time.

Basic Set up:

Gaal Dornick, a mathematician, is on his way to Trantor, the capital of the Galactic Empire, to meet with the scientist Hari Seldon.

This voyage that Gaal takes across the Galaxy is pretty loopy. It's a voyage through "hyperspace." What's that exactly? Well it's that region that is "neither space nor time, matter nor energy, something nor nothing." Confused yet?

The point is, really, that Foundation is another Sci-fi work that's full of voyages. The distances that are traversed in these cross-galactic journeys are huge. They're so huge we can't even begin to wrap our minds around them… or what it takes to get from point A to point B.

In this passage we'll find sci-fi's usual emphasis on science and pseudo-science. The "Jump" is a process through which people can cover huge distances in no time at all.

So the "Jump" may be something that Asimov has made up. But the point is, it's presented to us readers as a scientific possibility. Who knows? Maybe in a thousand years we'll also be able to "jump" through hyperspace like intergalactic bunny rabbits.