As they hide in a parking lot, Kyle explains to Sarah that an artificial intelligence defense network, known as Skynet, will become self-aware in the near future and initiate a nuclear holocaust. Sarah's future son John will rally the survivors and lead a resistance movement against Skynet and its army of machines. With the Resistance on the verge of victory, Skynet sent a Terminator back in time to kill Sarah before John is born, to prevent the formation of the Resistance. The Terminator is an efficient killing machine with a powerful metal endoskeleton and an external layer of living tissue that makes him appear human.