The film follows Kyle Reese, a soldier in a post-apocalyptic future with a war against the machines led by Skynet, who is sent from 2029 to 1984 by John Connor, leader of the Human Resistance, to protect his mother Sarah. When Kyle arrives in the past, he discovers that the timeline has been altered and Sarah has been raised by a reprogrammed Terminator.

References:
https://en.wikipedia.org/wiki/Terminator_Genisys