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 humans had been reliant on the Warp Drive that NASA had invented in the 21st 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 nearby galaxies orbiting our galaxy. The invention of the now popular Wormhole Drive opened the entire universe to humanity and they began exploring their entire galaxy and their neighbors.
The amount of distance it can cover is related to how much power can be put into opening a wormhole. It was discovered that, from the Milky Way, burning out a star the size of Sol could open a wormhole to anywhere within 100 million light years. The wormholes then sustain themselves for an indefinite amount of time. At the dawn of the Fourth Age, this was the limit, but in the year 14021, an advanced form of wormhole generation was developed, allowing for travel over 500 million light years in a single jump. The first test opened a wormhole to the edge of the Tadpole Galaxy. The technology only continued to improve.
Wormhole generation was invented at first to help the Confederacy turn the tide in the Second Galactic War but it was eventually put to use to help expand the human race and their allies among the universe.
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.