Terminator 1 and Terminator 2?

Question

How come in T1 the terminator trys to kill sarah connor, but in T2 he trys to save her?

Answer 1

The first Terminator is destroyed in T1. The Second Terminator is re-programmed (in the future) by John Conner to protect his younger self and his mom from the shape shifting T-1000 Terminator, played by Robert Patrick

Answer 2

Obviously, they're very different terminators. Only played by the same actor.

In the first Terminator film, it was sent to kill Sarah Connor in order to prevent John Connor from being born. It was destroyed in a factory and its pieces were discovered by Cyberdyne, creating different parallel universe for the apocalypse.

In the second Terminator film, the terminator was slightly updated from the original Terminator, was captured by the resistance, was programmed to protect only John Connor, and sent to the time of John's childhood to ensure his survival. The Terminator helped protecting Sarah Connor just because John ordered him to. Before John and his guardian headed for the ward to save Sarah, the Terminator had no care for Sarah's survival.