In the universe of Final Fantasy IX, Terra is the twin world of Gaia.
In an unspecified amount of time before the events of Final Fantasy IX, Terra underwent a terrible cataclysm that caused the majority of life to be extinguished. The Terrans managed to store their souls in suspended animation and remain dormant within Pandemonium in the hope that one day their culture would be restored. Garland, one of the survivors, created the Genomes, empty humanoid vessels that would receive the souls of Terra once Gaia had been assimilated into Terra. Garland hoped that the people of Gaia would eventually die out, allowing the planet to be absorbed by Terra, but then decided to take the Gaian genocide into his own hands