Rannoch is an arid, rocky planet that was the original home of the Quarians. During the Morning War, the Quarian's mechanical slaves, aka the Geth, rose up in a robot revolution and drove them off the planet. During the Reaper War, the Quarians and the Geth negotiated a truce and the planet is now shared between the two races. It is a prospering trade route that brings benefit to both Quarian and Geth economies. Of course, the only reason anyone visits the planet is because of the Geth. No-one likes Quarians.