Effectively the high ways of space. They are also called Subspace Pathways, Jump Points, and collectively the Path of the Stars or Star Ways
Due to the nature of gravitation fields, their are certain pathways, connecting two solar systems and to a lesser extent planets, where Warp Fields work at their best. These paths are marked by currents of warped subspace ways. Hyperspace Drives, skip traditional Warp Fields, and instead send the ship into subspace to use these currents like a boat to move faster and with less effort.
Hyperspace Pathways are the most commonly used forms of interstellar travel since their discovery. They are so widely used that most civilian ships are incapable of going into FTL anywhere but along these Pathways. There are however much faster forms of FTL not commonly used or known by the main empires.