The film begins with the audience seeing judgement day, and the machines attempting to seize control of the earth by killing all of mankind. The resistance is lead by John Connor and the machines send back a Terminator in order to kill him so that the war will not go in favor of mankind. We watch as Schwarzenegger, the original Terminator that was sent to kill John's mother, Sarah returns to a time before the war. This creates an expectation that he will, as he did in the first film, be the enemy of Sarah and her young son, John. However, by the end of the film, Terminator gives his life in order to protect John.
Thus the film is about the ability for change, and more importantly the necessity of change if mankind is going to survive. I'm not sure this was the allegory that Cameron and Gale Ann Hurd set out to write, but it is one that was created because of their commitment to the story that was in their imagination and their desire to bring it to life on-screen. What we see is a battle of technology. What is considered outdated battling what's new, and in the end it isn't the new technology that wins out. It is the heart and one's willingness to sacrifice for others that allows for the greatest victory to occur no matter what level of weaponry is deployed.
This film is also about relationship. The Terminator becomes a friend, and like a father figure to John as he protects him from the dangers of the world that attempt to harm him and take his life. This provides John with a relationship that he's been lacking in his life. It is also about redemption as The Terminator becomes the protector of the people he initially was sent to kill, this takes great trust from Sarah to allow this machine to even be in proximity to her and her son as it was trying to kill her in the first film. This idea is one of humanities ability to adapt and work with technology as the technology advances through modifications that cause it to work for humanity rather than against it. When working together, man and machine can co-exist, but the balance is one that is very difficult to keep.
