Astronomical distances and the impossibility of faster-than-light travel pose a challenge to most science-fiction authors. They can be dealt with in several ways: accept them as such (hibernation, slow boats, generation ships, time dilation – the crew will perceive the distance as much shorter and thus flight time will be short from their perspective), find a way to move faster than light (warp drive), "fold" space to achieve instantaneous translation (e.g. the Dune universe's Holtzman effect), access some sort of shortcut (wormholes), utilize a closed timelike curve (e.g. Stross' Singularity Sky), or sidestep the problem in an alternate space: hyperspace.
Hyperspace is sometimes used to enable and explain faster-than-light (FTL) travel in science fiction stories where FTL is necessary for interstellar travel or intergalactic travel. Spacecraft able to use hyperspace for FTL travel are sometimes said to have a hyperdrive.
Authors may develop alternative names for hyperspace in their works, such as the Immaterium (used in Warhammer 40,000), Z space in Animorphs, or "Underspace" (U-space), commonly referred to in the works of Neal Asher.
In normal 3-D space, the "shortest path" between two events A and B is by traveling in a straight line. Because of relativity, there is no such thing as universal time: so let the time be measured with respect to a clock whose motion matches the space-time path. Call this space-time path "P". Then the shortest path in space is simply the path in space traced by the space-time path P.