In the vision future explored by this show, humanity is divided into 3 factions.

• The oppressed Belters, an exploited Creole race of substistence asteroid miners whose excess production in extracted for the sake of the Inners, represented by Naomi Nagata, a genius black woman with a past among the rebellious OPA faction in the Belt.
• The Martians, a militaristic Republic in the midst of trying to teraform the Red Planet, represented to the audience by Roberta "Bobby" Draper, a martian Marine.
• And the Earthers, governed by the UN headed by Secretary General Chrisjen Avisarella, an Indian woman with a penchant for subjecting Belter terrorists to gravitationally enhanced interrogation techniques, and represented to the audience by Amos Burton, a big White brute who prefers to think with his fists, and our protagonist James Holden, a man conceived from the genetic combination of 8 "parents" from an Earth commune.

The only religion mentioned anywhere in the series is the Mormon Church, who have commissioned the Belters to build them a generation ship, the Navoo, the largest ship anywhere in the solar system which they intend to use to colonize other star systems. The Mormons are largely dismissed by other characters and fully ignored in later parts of the series. The series largely implies an absurdist view of the universe, where most of the characters are willing to use the violence they are capable of to get what they want, though some such as Holden tend to exhibit some empathy for the oppressed. There is a considerable amount of sexual content depicted, including homosexual relationships, especially among the Belters. The main technology that differentiates the world of the Expanse from our own is a nuclear powered spacecraft drive system called the Epstein Drive, capable of achieving massive accelerations with extreme efficiency. Such a technology enables humans to cross the massive stretches of space between the planets and the asteroid belt and rapidly colonize the solar system. The series is clearly trying to push a narrative of left-wing social justice with a patina of science fiction over the top of it.