With hyperspace a key component of The High Republic storyline, this article couldn’t be better timed, looking at amongst other things what hyperspace is and how the purgil introduced sentients to this other dimension.
The most rudimentary definition of hyperspace is a dimension of space used to travel across (typically) long distances. Essentially, the Star Wars galaxy exists in “realspace” (just as the Milky Way does), but at some point, residents of the galaxy discovered a dimension that broke past any speed barriers. This allowed them to travel far and fast, making space travel more accessible and traversable. To access hyperspace a ship needs to reach (and inevitably surpass) “lightspeed.”Reaching these speeds allows ships to basically break through the barrier from realspace into hyperspace.
In order to reach these speeds, a ship requires a hyperdrive — a propulsion system that would pitch the ship to lightspeed in order to “jump” to hyperspace. (Although ships often travel at far faster velocities than lightspeed once in hyperspace, something otherwise impossible to do.)