The geth are a humanoid race of networked A.I.s. They were created by the quarians 300 years ago as tools of labor and war. When the geth showed signs of self-evolution, the quarians attempted to exterminate them. The geth won the resulting war. This example has led to legal, systematic repression of artificial intelligences in galactic society.
The geth possess a unique distributed intelligence. An individual has rudimentary animal instincts, but as their numbers and proximity increase, the apparent intelligence of each individual improves. In groups, they can reason, analyze situations, and use tactics as well as any organic race.
Geth space is located at the trailing end of the Perseus Arm, beyond the lawless Terminus Systems. The Perseus Veil, an obscuring "dark nebula" of opaque gas and dust, lies between their space and the Terminus Systems.