Jörmungandr

Jörmungandr was created around a century ago as a symbol of unity during a time of global peace, with all nations sending their best engineers and artisans to aid in its construction. Even now, it stands as a marvel of engineering that is unreproducible and far ahead of its time. In fact, much of modern eitrcraft comes from craftsmen reverse-engineering what was used on the train. The train stands as tall as a small mountain, and its length stretches for miles. The inside is a city that rivals the capitals of other nations in population and sprawl. Furthermore, the train mostly maintains self-sufficiency with farms covering the roofs of the cars, and water reclamation systems working to both recycle used water and to catch and filter water from the exterior.
Currently, the train is seen as a normal part of the world by most, and stands as neutral ground protected by a global treaty forbidding the nations from using it to either house or transport troops.

The Trainborn

As the name suggests, the Trainborn are those who were born on Jörmungandr and they often take great pride in this fact. Due to the fact that the train circles the world, the Trainborn do not have a standard expected race or ethnicity and are thus incredibly diverse. Culture aboard the train is similarly varied, with elements of many other countries' cultures blended together present in it. One of the best examples of this is the common language aboard the train, a pidgin language which is often referred to as Trainspeak.
The train is governed by a council made up by the heads of the 5 Families, a term that refers to the 5 richest and most powerful families aboard the train.

Travellers

Travellers, sometimes known as Passengers or simply as Outsiders, are those who purchase tickets to board Jörmungandr. Generally, these people are using the train as a form of transportation, hence the name (though the name is applied to anyone not born on the train, even if they've moved on-board to live permanently). Tickets for Jörmungandr are not sold in the same way that regular tickets are. Instead of paying for passage to a particular destination, passengers buy tickets that allow them a certain amount of time on the train. Should a Traveler's ticket run out, they will be required to leave the train at the next stop. Should they fail to do so, they tend to be forcibly ejected, sometimes while the train is still in motion.
Furthermore,a Traveler's ticket functions as their ID upon the train, and is required for most things on-board. In the case that a Traveler is found without their ticket, they can be fined heavily and incarcerated. That said, there have been cases of this law being used to target "unfavorable" Travelers.

Type

Geopolitical, City-state