To simplify the notion, space can be visualized as a two-dimensional (2D) surface. In this case, a wormhole would appear as a portal through that surface, which leada into a three dimensional tube (the inside surface of a cylinder), then re-emerge at another location on the 2D surface with a similar portal like structure with respect to the entrance. An actual wormhole would be analogous to this, but with the spatial dimensions raised by one. For example, instead of circular outlines on a 2D plane, the entry and exit points could be visualized as spheres in 3D space, while the tunnel itself would be 4D.
Traversable wormholes were speculated to exist ever since the 20th century, and were confirmed to exist by the discovery of the Ring Network, which is comprised of more than a thousand stable wormholes.
The first wormhole encountered by humanity was the Sol Ring, a gate part of an ancient, although still functioning network of wormholes leading to many star systems with habitable planets. The ring was created by the protomolecule, an ancient pathogen sent towards Earth by an ancient civilization which sought the use of mankind as biomass needed for the protomolecule to establish the wormhole leading to the slow zone. Instead, the protomolecule, stored in Phoebe, was caught by Saturn's gravity and entered orbit around the gas giant.
It wasn't until several eons later that the protomolecule would be discovered and subsequently released on Eros, where it consumed as much biomass as it could, almost killing Holden and Miller, which were present there. With this amount of biomass, it was revealed that the protomolecule had the ability to create a hive mind of sorts, which integrated itself with the computer systems of Eros station.
Following the descent of Eros Station to the surface of Venus, the protomolecule began rapidly reshaping the planet. Observers throughout the Sol system observed these changes with great interest, but, despite the wealth of data, the objectives of the alien organism remained obscure.
The military science vessel Arboghast was tasked with observing Venus from orbit and relaying instrumental data to the UN. Eight months into her mission, the Arboghast received or emitted a brief radiation pulse of unknown nature and origin that interfered with all observation telescopes in the non-visible spectrum. Immediately following this, the entire vessel was disassembled into its structural components, down to the level of screws and bolts, methodically and with no discernible mechanism of action. The crew of 572 personnel were lost to vacuum exposure.
The protomolecule spent a little more than a year on Venus preparing itself, before it launched a massive complex of structures just outside the orbit of Uranus and built a thousand-kilometer-wide object known as the Ring. This is the final stage of the protomolecule life cycle: to convert itself to into a wormhole leading to the slow zone and Ring Station.
Wormholes have been demonstrated to be feasible by the alien civilization, which managed to build an entire network connecting many systems. Although extremely stable, their physical capabilities can be overwhelmed if too much foreign matter attempts travel through them.
The overwhelmed wormhole would not collapse. Instead, it would strand all spaceships engaged in transit in its throat, thus in higher (4D) space, forever severing their link with known space. This astrophysical phenomenon was discovered by Naomi Nagata, which managed to weaponize this "weakness" and defeat the Free Navy. Even so, it is unknown exactly how very large quantities of foreign matter affect the wormhole and leads to it being overwhelmed.
Because of this danger, transit through the wormhole network is regulated by the Belt Union, as an attempt to avoid any gate from being overwhelmed.
Although the process of creating a wormhole is speculatively known, it requires the existence of exotic matter, which was confirmed to exist due to the Ring Network being comprised of perfectly stable wormholes, which haven't collapsed since their establishment, eons ago. Along with exotic matter, a wormhole might require some degrees of quantum manipulation to ensure their survival over long periods of time.
The throat of the wormhole is the corresponding tunnel through higher space which links the two entrances.The lenght of the wormhole's throat is relatively short, especially when compared with the actual distance between the points it links.
When a wormhole's physical capabilities are overwhelmed, it is believed that the ships remain stranded in its throat.