Halo: Reach is a shooter game with players experiencing gameplay from a first person perspective.

A system of single-use equipment found in Halo 3 is replaced by reusable and persistent armor abilities, which remain with a player until they are replaced: examples include active camouflage and a sprint ability.

Reach takes place in a futuristic science fiction setting during the year 2552, days before the events of the 2001 video game Halo: Combat Evolved. Humans, under the auspices of the Uniited Nations Space Command (UNSC), have been waging a long war against a collective of alien races known as the Covenant. By the events of Reach, almost all of humanity's interstellar colonies have fallen. Reach is the UNSC's most fortified world after Earth, and serves as a military and intelligence hub.

The game follows the actions of Noble Team, a UNSC special operations unit composed of elite supersoldiers known as Spartans. Players assume the role of an unnamed new addition to the team, identified by the call sign Noble 6. Noble Team's leader is Carter-259, a no-nonsense soldier. His second-in-command, Kat-320, has a bionic arm; together Carter and Kat are the only two remaining original members of Noble Team. The other members include heavy weapons specialist Jorge-052, Emile-239, and marksman Jun-226.