The Gates break the space-time continuum and allow an almost instantaneous FTL travel between two points of the Universe. In the center of the gate there is always a rift, which is supported by a pair of stabilizing rings, each connected to the thick outer contour ring with stabilizing microdrives, where the Helmerich generator is situated, which is producing the T-matter for the rift and delivers it via a collection of tubes, in order to maintain it open.
The Gates became the main way of traveling due to their cheapness. It is much more efficient to keep the pathway open that to curve the spacetime each time a travel is needed, like the warp drives do (which also exist, but are rarely used, as it takes months to generate enough T-matter for one jump)
The opening of the gate is an especially tedious ask. First one needs to open the wormhole using the first gate to the specific output location. The opened wormhole is one direction only and relatively small, and the assembly team needs to transfer all the materials for building the paired gate on the other side and as quickly as possible construct a second one. The wormhole without a gate on the other side consumes an enormous amount of T-matter to ensure stability of the output location. In case the construction team takes too much time, the first gate might run out of T-matter, and the wormhole will close. It is almost impossible to redirect the gate to the same output location, and when talking about long distance travel - even to the same star system, making the Gate construction a risky venture.