Jump Drives are a type of space-folding drive. They work by dumping a massive amount of energy and doing a 'dimensional' style travel, in which the vessel is briefly able to access every point within 3D space. The ship can then emerge anywhere else almost instantly.

A major problem with this, however, is that the ship doing the Jump is unable to 'look before it leaps'. It is a problem both of sensors being unable to function in a higher dimension, and the ship unable to loiter long enough in the higher dimension to scan its destination. As such, for Jump to be safe, there has to be a “JumpGate” at the other side.

JumpGates are not literally gates; there is no passageway the ship flies through. Instead, it's a small space station with a Comm Relay built into it. The station sweeps particles and other objects out of the way, keeping the 'landing zone' clear. The drive that wishes to Jump to the gate will establish communications with it first. After getting clearance, the Jump coordinates are confirmed, and the operation can be performed.

Any Jump-capable ship can Jump from any point, not requiring a gate to start a jump. The gate is only required for the destination.

There's the obvious limitation that Jump can only go to a place with a Gate. It is, technically, possible to go to a place without a gate, but such would be very ill advised. Even microscopic particles in the destination can cause severe or even catastrophic damage to a ship; Jumping into another ship or a planet would cause massive amounts of destruction.

A Jump drive could, theoretically, be used as a weapon of war; however, aside from that being a war crime, it would also be increadibly, stupendously expensive. Which brings us to the next point…

Jump drives are incredibly expensive. GDP of several planets grade expensive. They must be large, they must have an enormous energy output, and they require a great deal of internal infrastructure to support Jump. As such, there are relatively few Jump ships and almost all of them are owned by 'the public', such as Jump Ferries or military ships.

All told, there are certainly less than 100 ships in the galaxy with Jump Drives. Probably in the neighborhood of around 60 in total, perhaps upwards of 70 or 80.

Jump Drives have an interesting role in intergalatic travel. A gate can be either part of an exploration ship or towed by a cargo ship. About 520 years ago, an expedition was engaged to cross the deep black from the Andromeda Galaxy which is our home, to the Milky Way Galaxy which is our nearest neighbor. The trip took about 500 years by high efficiency Ripple Drive, towing a Jump Gate with it.

By towing a Jump Gate, the expedition was able to park the gate in the middle and use it to briefly return home in order to resupply or swap crew. Crews would be rotated on and off, so that no one person had to man the ship for more than a couple years. It was incredibly dull duty, but necessary. in the end, they were able to reach the Milky Way and leave the Gate there for ease of future travel.

Now, Jump Drives allow for instant travel between the galaxies.

So if there are only a handful of Jump ships in the galaxy, what good are they?

The answer: Jump Ferries. Jump Ferries are massive carrier ships that take other ships through the gate. They have docking compartments for small to mid size freighters, and the ability to tandem-jump with large- and super freighters. Additionally, they can take passengers that board and de-board by local shuttle.

Jump Ferries are usually owned and operated by the CSS, though there is a fee to go across using one. The fee is pretty reasonable and always cheaper than traveling the distance using more conventional drives. In addition to the Jump Gate at the edge of the Milky Way galaxy, there are about 20 gates scattered about Andromeda. To cross Andromeda using Ripple Drives would take about 30-some years; using a gate, one can travel several days to the gate, and then Jump across, thus cutting travel time considerably.