How do you travel faster than the speed of light, especially when it's supposed to be impossible?
There's two ways of looking at this. The first one is the less-fun one: it's really just kind of pragmatically necessary in a science fiction game developed by some geeks who loved the works of Lucas and Roddenberry and wanted to play with ships. While it might have been challenging and interesting to try to work within our current understanding of physics - generation ships, relativistic effects, only using fold space - but we just didn't want to.
The second is to imagine how such cheating might look. We decided to muck about in "hyperspace", as so many of our favourite authors have. The model we use for superluminal travel involves creating a wrinkle in space-time, setting a vessel on a little stable patch of fake space-time (aka: hyperspace) in that wrinkle, and surfing that wrinkle faster than reality.
When ships are in hyperspace, they are both easy targets and vulnerable. They're easy targets because hyperspace lights up the ether (space-time) as much as a celestial body, and because boundary effects between the hyperspace and regular space-time make the vessel's vector very predictable and the vessel's equivalent length (in direction of travel) to be proportional to their speed. They're vulnerable because hyperspace is both fragile and unstable. Energy transiting from regular space-time into hyperspace (such as a weapon blast) is typically magnified by a factor of 10 (because we're lazy, mathematically). Matter transiting from regular space-time into hyperspace (such as a missile or projectile) also has momentum effects magnified by a factor of 10, and a chance of shattering the hyperspace "wrinkle" If hyperspace is shattered, the vessel inside dumps into regular space-time as a gorgeous spray of colourful particles.
Inversely, energy leaving hyperspace is generally barely detectable and unfocused. And matter ejected from hyperspace turns into the aforementioned colourful spray. So, if you ram an enemy ship while you're superluminal, you're not going to take them with you.
Due to the dangers of hyperspace, most superluminal vessels tend to prefer to travel in space lanes. Not actually designated in any specific way, space lanes are simply where other ships have travelled already, recently. The idea being that while etheric sensors might not give sufficient warning to duck some particular small chunk of matter in the void (or pirates, or whatever), it'll give enough warning for the next ship. As ships flinch slightly away from problems, which translates into huge distances in regular space-time, the line of ships following end up with a trial-by-error fairly problem-free route between common destinations.
A ship travelling superluminally alone can only really be detected in terms of mass and velocity. Ships travelling together or in a well-populated space lane appear to smear together and are very hard to distinguish instantaneously. A mathematician observing a space lane for a given segment of time can deduce the probable masses and velocities of the vessels in the space lane via Gaussian statistical analysis, but not until after the fact.
To travel superluminally for any duration requires shields, due to the damage inflicted by stray particles distributed through the transited void. This damage is usually minimal in an established space lane. For vessels bushwhacking through untrammeled void, the referee may decide to inflict some annoying harm on the ship's shields proportional to both the superluminal speed and the size of the vessel.