A nexus is a sentient-made wormhole. The Nexus Gates harness this ability. They are also commonly called jumpgates.
The tek for the Nexus Gates was a result of the research into jumpdrives. Utilising the same tek allowed for the production of the Grid as well.
At the high point of the IGC, they maintained dozens of Nexus Gates around the cosmos at strategic point, and would charge people for their use. Even though using a Nexus Gate is prohibitively expensive for a regular person, traders and cargo haulers can actually save money by transporting themselves and their goods through the jumpgates.
In the wake of the Intergalactic War, there are only about half a dozen remaining gates. Only two are still under the control of the Intergalactic Confederation.
It's not necessary for there to be a gate at the "receiving end." The jumpgates are programmed with coordinates and can open a rift to anywhere in the universe.
Rumours of the Confederation sending people they harboured some resentment against into the dead reaches of space are completely unsubstantiated with evidence.