Terminator 1, 2, and 3 are direct sequels to each other, with Sarah Connor Chronicles, Salvation and Genisys being alternate possible futures.
In Terminator 1, Skynet was created and tried to destroy the humans, but John Connor taught the humans how to fight. Then, Skynet sent T-800 to kill Sarah, and John sent Kyle Reese to protect her. They destroyed the T-800, but his arm and chip were intact.
In Terminator 2, Miles Dyson used the T-800 arm and chip to create Skynet earlier than expected in 1997, and Skynet sent T-1000 to 1995 to kill John Connor, but John of the future reprogrammed a T-800 to protect his past self. Sarah and Miles destroy the Cyberdyne Building, stopping Skynet from being created and stopping the Judgement Day in 1997. T…Read more >