Portal Network

The Portal Network is a series of interconnected wormholes that bind together a number of planet-communities. A traversal from one planet to another may require between one and five jumps through portals, depending on the distance involved and the number of rings that must be passed. Each ring is defined as a set of planets all accessible to one another through a single jump.
At the center of the network is Icy Foyer. Icy Foyer is a featureless and atmosphereless moon composed primarily of frozen nitrogen. Icy Foyer is also home to five of the Gates, each of which connects to a different ring. In a prior conflict, nukes were employed on Icy Foyer, which means the platform which hosts the gates is still irradiated. As a result of that and its atmospherelessness, travel through Icy Foyer is rare and carefully measured.
Known Worlds:
What follows below is a brief description (organized by ring) of the worlds that are known and have been visited in the Maeglin Gate Network. More detail may be known about worlds which have been visited, but no information is available on unvisited worlds except for the password to reach them.
Rainbow Ring
The Rainbow Ring is humanity's most extensively-explored Ring. Nordic Frog Beach, humanity's new home is here. Humanity interacts with Ischyro on Cubegarden, a nearly-habitable world of peaceful grasslands. Important biological research is done at S.E.E.L., a Dyson sphere where the Maeglin stored valuables. A few human colonies scatter around Tandoori, a dangerous desert planet inhabited by meat-eating scavengers. Triton, an icy moon on the edge of the Sol System, is also linked here. This Ring links to fourteen other worlds, some of which have been lightly explored and some of which have never been visited.
William's Report provides some additional details on the Rainbow Ring.
The portal that leads to the Diamond Ring is somewhere on S.E.E.L., but no one knows conclusively where.
Silver Ring
The Silver Ring is home to "Spideyworld", the home planet of the Anansi. Spideyworld is covered by glaciers, but has a few areas where the temperature allows for rivers and lakes. A second destination, a stormy moon inhabited by the Anansi, orbits an unusually-warm gas giant. The Maeglin Archive, an ancient space station claimed by Myrmidon, also is in the Silver Ring.
To reach the Maeglin Academy, travelers must enter the Silver Ring and traverse a Maeglin security installation (the Customs).
There are three other worlds in the Silver Ring that have yet to be explored.
Red Ring
There are five worlds in the Red Ring, and for the most part, the Ring is avoided by both the Humans and the Anansi.
It is known that there is a destroyed planet that once was a unified A.I., a failed colony on a swamp planet whose native vegetation saps intelligence, a destroyed, irradiated, tiny rock in the Sol System, a gas giant, and a planet primarily made of naturally-magnetic ores.
Lightning Ring
Humans have only ever been to two of the planets in the Lightning Ring.
Ifera's Journeys briefly recounts the so-called "Deadly Wasteland" that Ifera passed through on her way to the Maeglin Nursery. In addition, humans have visited Haaloct, a harsh and unforgiving world where all the life evolved beneath the surface, which is scoured by high winds and deadly radiation. Haaloct is known to be home to the Neblins, a savage but apparently-sentient race of small humanoids currently going through the Stone Age.
There are six other unexplored worlds in the Lightning Ring. 
Yellow Ring
The Yellow Ring is the least-visited out of all of the Rings. Ifera's Journeys mentions visiting the Maeglin Crucible, but doesn't contain much detail about the planet beyond the native vermin species.
There are four other unexplored worlds in the Yellow Ring. It is known that one of them is a Maeglin Installation known as the Power Plant.

Utility

The Gates can be used to instantly travel to the connecting Gate which a user opens a portal to. In order to use a portal, one must connect to it with a networked wireless device as if it were another computer or a router. The user can open a portal to any world they want, but it comes from a preselected list of celestial bodies outfitted with a matching linked portal. The user can also close an active portal they are connected to. 
A person can simply walk through an opened portal and they will arrive at their destination with no intervening time having passed. 
The portals are 3 m (10ft) in diameter, which limits the size of the object or vehicle which can pass through them.
Essentially, the portals open up several dozen worlds of varying habitability and danger to relatively accessible pedestrian traffic.

Access & Availability

Anyone with a wireless network connection can use the Gates by typing in a five-word password that accurately describes the destination planet. However, the Gates are also in immutable locations, which means some areas and governments may have set up security outposts around their Gates.
The Gates on Nordic Frog Beach, Spideyworld, and Tandoori are monitored but unguarded, which means they are free for anyone to use.

Complexity

The Gates are immeasurably complex. They were created by psionic Maeglin artificers at the peak of the Maeglin Empire. They use countless technologies not understood by humans
What is understood by humans is that they utilize quantum entanglement. Any Gates that are connected are essentially treated as if they are all in the same location. Walk through one side and come out the other.

Discovery

The Portal Network was discovered by Scrud, as well as the crew of the Albatross, the year before Nordic Year Zero. She was under the employ of Ikumi Higa, a warlord from Mars, but that relationship was terminated when one of Scrud's allies dropped a bomb into a Martian space station. However, Scrud and her friends had already gained significant knowledge of the Gate network when the Martians were provoked. She was able to defeat the Martian attack force and claim the Portal Network for the free peoples. With a number of exowombs, a colony was jumpstarted on Nordic Frog Beach and the Network was in peace.