A wormhole, or as it is known by its official name, Einstein-Rosen Bridge, is a phenomenon that connects two points in space-time, a shortcut in the universe.
Humans had long since wondered if wormholes could be used to cross the universe in seconds. In the year 5050, a series of space-time anomalies were found on Karine Planet, which turned out to be wormholes leading to parallel universes. These unstable anomalies were the inspiration to create the technology to open the first stable wormhole to the middle of the Pleiades Cluster in 9952. The wormhole was stabilized with exotic matter of negative density.
For thousands of years, the FUSS had been reliant on the Warp Drive that they invented in the 23rd century. Improvements were made on the warp drive, but they'd only been able to explore just the Milky Way Galaxy, and had paid a few visits to a few satellite galaxies. The invention of the now popular Wormhole Drive opened the entire universe to humanity, and they started to set up wormhole-lanes that had to be set up first. Wormhole lanes were being set up across the cosmos, and a lengthy Milky Way-Andromeda wormhole highway was complete in the 12400s.
The amount of distance it can cover is related to how much exotic matter is used to stabilize it, and how far the end and start-points are. Most wormholes traverse many hubs, and other distances that would take much longer with the standardized Warp Drive.
Wormholes go through the 4th dimension as illustrated in the image above. While wormholes could theoretically be used to traverse the 4th dimension, gravitational forces force whatever enters to go through in the direction they went in, unless they close mid-jump in which case, matter inside becomes stranded in an area disconnected from our plane in 4D space. Foremholl, an anomaly that could possibly be a wormhole without a destination, could be a portal into the 4th dimension, however it goes nowhere and probes loose contact at a certain depth.