A good space opera setting needs starships, and starships need some means of getting around---an FTL drive. Unfortunately for would-be interstellar travelers, the laws of physics have this annoying speed limit in C, the speed of light, unattainable by any object or particle with any mass at all. Thanks to relativity, as an object with mass approaches the speed of light, its overall mass-energy approaches infinity, requiring ever more energy to continue accelerating. And this doesn't even get into the other funky relativistic effects, like the time dilation and spatial distortion perceived from different reference frames. A proper FTL drive needs some way to circumvent the light barrier---a loophole in the laws of physics.
The traditional FTL drive is the "warp drive" (named as such in Star Trek; the "hetch drive" from Farscape probably operates on similar principles, to say nothing of the unmentioned FTL technology used in the classic Battlestar Galactica series). The idea behind the warp drive is actually pretty simple: if you can move space and time around the ship, rather than moving the ship itself, relativity and the light barrier ought not to apply. So you create a field of curved space-time (and nothing curves space-time quite like gravity, so the field is just an artificial gravity field) in the shape of a "bubble" around the ship, and then you tweak the shape of the bubble so that you're putting less space-time in front of the ship and more behind it. Voilà, FTL travel. (Major conceptual problem: in real life, it's not likely that a graviton could propagate through space any faster than a photon, so how is the warp bubble as a whole moving faster than light? Who knows? Who cares? It's science fiction.) Generally speaking, warp drive is slow for an FTL method: cruising speed is usually a few hundred times the speed of light, maybe a thousand times lightspeed at the outside. (For example: it would take the U.S.S. Voyager seventy years to get from the Delta Quadrant back to Earth using conventional warp drive; a Peacekeeper Command Carrier leaving the Uncharted Territories at maximum hetch-speed could reach Earth in sixty years.)
If the sci-fi setting needs a more unified galaxy where speedier travel is possible, the go-to technology is hyperspace. Star Wars and Stargate use hyperspace travel (as do Leviathan starships in Farscape, although they call it "Starburst".) Star Trek calls it "transwarp" or "quantum slipdrive" ("slipstream" seems to be a common alternative name for a hyperspace jump). The "jump drives" from newer Battlestar Galactica would also seem to operate on this principle, but in a more limited fashion. The upshot: a hyperdrive doesn't so much generate a field as a portal (Stargate explicitly refers to a "hyperspace window") through which the ship transitions ("jumps") into a higher dimension (hyperspace), travels at hugely FTL speeds, and then transitions back into "realspace" at the end of the jump. Hyperspace is really fast. In Star Wars, ships can cross the galaxy in a couple of days. In Stargate, there are lots of different hyperdrive engines, depending on the technology and the power source: Goa'uld hyperdrives seem to be about as fast as Star Wars hyperdrives, while Asgard and Ancient hyperdrive engines are capable of traveling between galaxies in a matter of weeks or days (depending on whether the ship is drawing power from a naquadah reactor or a zero-point energy module).
Last but not least, there are wormholes (or "Einstein-Rosen bridges"), shortcuts in space-time which (if traversable) would allow a ship to go anywhere in the universe, at any point in time, instantaneously. So unless you want the game to be all about time-travel and how the player characters can screw up causality or mess with the butterfly effect, it's probably not a good idea to put this technology into the players' hands. It would cause problems faster than you can say "grandfather paradox". No TARDIS for the party.
In the Primus Galaxy setting, FTL travel speeds are more like Star Trek: the FTL technology is basically a warp drive, although the in-universe name for it is "subspatial induction drive", often called a "subdrive" for short. Technobabble aside, a typical starship with engines in good repair, moving at cruising speed, can cover about three light-years per four days. Ships with military-grade engines are quite a bit faster, able to cruise along at two light-years per day. This is the foundation for all interstellar travel in the campaign world.
That said, this setting has three major competing civilizations, all of them looking for the next big military edge---so you just know that a hyperdrive engine would be the holy grail for whoever manages to invent one. It would make the farthest corners of the Primus Galaxy instantly accessible to who whoever controlled the technology, and it might even open up the potential for intergalactic exploration. (To a science fiction game, this would be functionally equivalent to a party of adventurers in a fantasy game acquiring their first airship. Naturally, it has to happen at some point down the road.)