The game is set in humanity's future, in a galaxy that is not our own. Nobody alive knows the full story. What follows is the legend of the Exodus, as the settled worlds tell it.
Earth was dying. A climate crisis had passed the point where staying was an option, and the only way to survive was to leave. In its final decades humanity pooled what it had left into one multinational effort and built a wormhole generator. It stayed on Earth, and it could be fired once.
By then humanity had space travel, and most of the remaining effort went into ships people could live on. What began as one effort split along political lines. Nations, corporations and foundations each built their own fleet, and by the end there were four.
At the heart of every fleet was an ark, a vessel built to carry a whole population and everything needed to start again. Around the arks flew everything else the fleets could assemble: freighters, escorts, survey craft, mining ships, anything that would fly. They loaded as much as they could carry and as many people as they could take.
On the day of the Exodus (the official name; everyone else says the crossing) the generator fired. The four fleets went through together. The wormhole was meant to open onto a surveyed star system in the Milky Way, the best candidate for a habitable planet. It did not. The wormhole closed behind them, and the sky on the other side was wrong.
The ships' navigation computers could not fix a position against any star catalogue on board. When they matched against the galaxies instead, the largest object in the sky resolved as the Milky Way seen edge-on from outside, with its two companions. Fixed against it and the rest of the Local Group, every ship returned the same answer, and the astronomers confirmed it by hand: the Andromeda galaxy, two and a half million light years from home.
Earth is still in their sky. Its light is two and a half million years old, from before there were people on it. No word has come from Earth since, and none can. The survivors reset the calendar. Year zero is the year of the Exodus, and the years since are counted AE, After Exodus.
The survivors tried to build a second wormhole and could not; they lacked the materials, and by then most other things too. What they built instead were smaller versions, small enough to fit aboard a ship, and they called them warp drives. A warp drive cannot take anybody back to Earth, but it was enough to start looking around.
Ships went out, found new systems and built stations, the fleets spread farther apart, and over time the four went their own ways and became the four factions. Humanity in Andromeda lives in space. The arks became the first stations, and stations became the pattern. Planets are worked, not lived on, with one exception: Eden, the only garden world anyone has found, settled by the Conclave.
It is 312 AE. Enough time has passed for the fleets to settle, build, fall out, trade and fight. Not enough time to have explored more than a fraction of the new galaxy. The frontier is close, and it is mostly empty.
You're nobody special. A pilot with a small ship and a licence to mine, starting out in Sora, in Federation space. The belt you cut ore from is about as close to land as most people get.