A Giftia is a type of android with a humanoid body that has been developed by Sion Artificial Intelligence Corporation (abbreviated as SAI Corp.), which is said to be the most accurate imitation of human life that the world has ever seen. Giftia would be indiscernible from humans if not for one crucial aspect of their existence: their lifespan. Giftia can only "live" for a maximum of 81,920 hours (approximately 9 years and 4.3 months), after which their programming becomes corrupt due to failed attempts at overwriting old information.
If a Giftia is not retrieved and deactivated before their lifespan runs out, there is a chance that they could become "Wanderers." When a Giftia becomes a Wanderer, they act only on instinct, not on memories. They often become violent, and because their limiting features fail, they also become incredibly strong and fast.
SAI Corp.'s Terminal Service is a branch of the company created to attempt to retrieve Giftia before they become Wanderers. Typically, retrieval is an easy, non-violent process, though occasionally a deadline is missed and the Terminal Service that is responsible for that region is required to recover the Giftia-turned-Wanderer by any means necessary. Giftias never return their memories after being deactivated, In the anime it has been said numerous times that the Giftias can't regain their personality and memories.