A hyperspace beacon is a permanent satellite or space station which is stationed
in the umbra, or hyperspace, just on the other side of a jumpgate. It collects radio and tachyon signals beamed through the jumpgate from realspace, then rebroadcasts them through hyperspace as a tachyon carrier wave. Picked up by matching hyperspace beacons next to other jumpgates in nearby star systems, these tachyon signals enable real-time communication between far-flung star systems (collectively known as the FedNet).
They also serve as navigation signals through hyperspace, enabling starships to safely travel from system to system. By linking star systems together, the nature of correspondence magick actually shrinks the effective distance between them through hyperspace, noticably shortening travel times between systems along the more heavily-traveled routes. This is why, while it's certainly possible to travel "off-beacon" from any one system to any other, it's shorter and safer to travel along well-worn shipping lanes, even if they seemingly take you some distance out of your way compared to a "direct" point to point path.
Some hyperspace beacon stations at the more populated and popular systems are permanent, manned space stations, with a crew running into the dozens: a mix of technicians to keep the communication and navigation gear in good repair, and traffic-control officers directing space traffic to keep ships from colliding with each other in the dense transit queues lining up to enter the jumpgate from the hyperspace side. Other stations are unmanned, but visited on a regular basis by maintenance crews in service vessels.