Despite covering a large expanse of the Milky Way Galaxy, much of the Orion Sphere is unsurveyed and unexplored. Even within Faction territory, the sheer number of stars that are present means visiting all of them for even a cursory survey would take a huge investment of energy and time. Spacefaring species tend to confine the majority of their exploration to solar systems that look like they could contain interesting things - usually determined by the spectrum of light that their stars emit and whether any planets had been found by astronomic observations.
Less interesting stars - those which are too large or small to support a habitable planet, or with no evidence of planets or of carbon in their emission spectra - are visited or explored infrequently. When these systems are visited and partially surveyed it is usually by accident, such as when a warp drive malfunctions. Pirates and free merchants are more likely to visit unexplored systems, perhaps to scout out potential boltholes or base sites, try and find rare elements or turn up some ancient ruins or artefacts. More regular starships and Faction forces may end up in such systems following up on a lead or chasing these miscreants.
Conventional warp-powered craft can take weeks to reach a star, and even more time visiting all of its planets, so it has not currently been deemed a worthy investment to explore lower-priority solar systems. With access to a faster means of transport however, it could be worth plumbing the unknown depths of the deep void.
Unexplored systems that have been identified on astronomical surveys are usually given a UXS (UneXplored System) designation, followed by their Sector and a number - such as UXS-Grus 7894. Once the system has been explored, and the data released, the explorers have the right to name the star, and that name becomes the new designation. The previous UXS number goes back into circulation and can be applied to newly catalogued stars.