Technology:
Propulsion:
Normal Space:
Most normal space travel is done with Ion Engines. The principle is pretty simple: Use magnets to throw hydrogen nuclei out at near light speeds. Basically, it's a really simple system, but it uses quite a bit of power. (No, they are in no way generators, unlike most scifi. Personally, I think having engines generate anything other than thrust is a stupid idea.)
Subspace:
Faster than light travel is, as we know, impossible. So, the trick isn't to travel faster than light. Instead, Ships move through 'subspace' which is a fancy name for moving in the fourth dimension. The basic principle can be explained this way:
Take a piece of paper, and draw a stick figure on it. Now, bend the paper into a U-shape. If the person were to move across the paper, it would take them a while to. However, if you pick them up, and move them in the third dimension, and it takes less time. Now, with subspace it's the same way, except that there's the combined effect of being able to 'crumble' space time (contract in front of you, and expand behind you) that give an effect of moving faster.
In Subspace, gravitational 'eddies' and mass 'shadows' exist. The forth dimension is the one where gravity 'lives' (as much as light 'lives' in a higher dimension), so changes in gravity cause vast sweeping changes in subspace, and vice versa. Orriginally, it was thought that subspace could be used as a weapon, one that could destroy planets, and end the war quickly, but the problem is that it's impossible to predict how changes in subspace will affect normal space, and it's even possible to create a gravitational wave that travels billions of lightyears, destroying everything in its path. (insert testing horror stories I haven't written here.)
Your 'speed' in subspace depends on you 'depth'. Basically, the farther removed from normal space you are (the deeper in subspace) the faster you travel. However, the deeper you are, the more the gravitational eddies take hold, and the more subspace tries to crush your ship.
Entering subspace involves the precise bending of gravity to create a wormhole of sorts to enter subspace. If your subspace field collapses while in subspace, you are violently thrown back into normal space. Also, it's possible to get stuck in 'limbo' (simultaneously entering and exiting subspace) which causes horrible gravitational shockwaves and turns your ship into a singularity. (a.k.a. a "black hole")
Metaphasic:
Metaphasic technology is, simply put, the best thing since sliced bread. It's also next to impossible, and no one even knows it exists, except the handful of researchers who created it. The theory is "simple": Use two subspace drives to allow a ship to remain in limbo, collect the tacheon particles that form up in between the subspace fields, and focus them to form a wormhole into 'hyperspace' or the 11th dimension if you prefer. You pop into hyperspace, and then exit into subspace again... but this time in a new place, instaneously.
The downside is that it takes great power, two complete subspace drives, and you need exit coordinates. What really sucks is that the only way to get those coordinates is to enter hyperspace, and take a look. (you can get your coordinates, and that of your surrounding area pretty easily, but you can't predict the hyperspace coordinates of the planet a few million kilometers from you. You need to go there and take another look. It has something to do with quantum mechanics.)
Right now, there is only a handful of ships whice can handle the stresses of metaphasic travel, and even fewer that have all the technology required to find coordinates. Basically, it's travel that exists in theory, and has worked a handful of times in practice by black projects conducted by the League.