Syfy's The Expanse is more than just a science fiction show about people traveling the solar system in spaceships. It's also a series that covers a wide range of topics, such as politics, poverty, oppression, discrimination and the struggle for resources in harsh environments.

On The Expanse, mankind has made great strides in space travel, and as a result, has colonized the solar system.

The series, which takes inspiration from a series of books by James S. A. Corey, presents a world where factions make up most of the population and where most people belong to one of these specific groups.

Here's a guide on the different factions from The Expanse, as well an explanation of what separates them from other groups.

The United Nations And Earthers

The United Nations, which consists of Earthers (those born on Earth and still living there), controls both Earth and the moon. Although based on their home planet, the United Nations also has facilities in Lovell City on Luna (the moon). The United Nations also controls Earth's military, the United Nations Navy and the United Nations Marine Corps.

The United Nations' leader is the Secretary-General, Esteban Sorrento-Gillis, with Sadavir Errinwright acting as undersecretary and Chrisjen Avasarala as assistant undersecretary.

Earthers see themselves as above most other groups, and are openly prejudiced against those not born on the planet, particularly the Belters, who they often don't even consider human. This attitude often affects trade, particularly for water, which is the most valued resource in the solar system. Earth currently holds most of the expanded world's water, which gives it control over much of the galaxy's goings-on.

Although Earth has a great deal of technology, it's still not as a advanced as the technology held by the Martians, Earth's main rival in the solar system.

The Martians

The Martians are those humans who colonized Mars and created permanent settlements there. They strive to terraform the planet's surface so that it more closely resembles Earth. They are led by the Martian Congressional Republic, which is often in conflict with the United Nations. This means that its people are also constantly in competition with Earthers.

However, in a fight, Mars would probably win, because although it has a small population, the environment Martians grew up in make them extremely tough and capable of living on fewer resources. It is also well-known that the Martian Congressional Republic Navy is more technologically advanced than the United Nations' military divisions.

The conflict between Earth and Mars becomes even more of a problem when Martians get blamed for attacking a Belter ship. However, the United Nations on Earth still hopes to avoid war, because they know it's a war they cannot win.

Martians and Earthers, though, do share one common trait: they both actively discriminate against and oppress Belters.

The Outer Planets Alliance (OPA)

Although seen by most other factions as a terrorist organization (and indeed the OPA finds its roots based in terrorism), this faction eventually becomes a loose government for those living around the asteroids and moons of the outer planets (except for Ganymede), with Fred Johnson as its leader.

However, even the OPA's terrorist roots had a solid mission: it sought to fight for the rights and interests of the Belters, because no one else seemed to care about them. This often puts the group at odds with the Martians and the Earthers.

The groups that comprise the OPA are generally made up of separate cells, such as the student group the Far Horizons Foundation, and the organization generally remains more of an institution of separate smaller factions than a singular, cohesive organization.

After false accusations arise about Mars' Navy attacking a Belter ship, OPA members and sympathizers start protesting on Ceres: eventually those protests become violent, and grow worse thanks to other factors, such as a lack of air and water there. This flings Ceres into utter chaos.

The Belters

The Belters aren't as much of a political faction as the OPA, but they get their name from being born in the Asteroid Belt, which makes them different from both the Martians and Earthers. Because they have spent their lives in low gravity, their bodies are different, with elongated limbs, a longer spine and bigger heads. Although this means that their bodies are well-suited for space, this also prevents them from ever landing on the surface of Earth or Mars: the gravity on those planets is too harsh for their delicate forms.

The Belters even have their own language, a combination of English and physical signs, something they adapted to communicate with while spending long hours strapped into space suits.

Unfortunately, Belters also have problems with pregnancy, because their abdominal and uterine muscles never fully develop due to low-gravity conditions. Pregnant women often temporarily relocate to Ceres, which has a spin gravity that allows for more successful births.

All of these things make the Belters different, so much that the Martians and Earthers treat them as a separate species and look down upon them, which often results in their oppression. They provide many resources to Earth and Mars, but those two planets treat them almost like slave labor, so they receive much less in return. Their lives are a constant struggle for prescious resources, such as water and air.

The Expanse airs Fridays on Syfy. The network also recently announced the series will have a second season.