There are two types of twists, at least that I can think of. The first being one that the in-universe characters are aware of, and the audience needs to be brought up to speed. Think of Psycho and Identity. With Psycho, we do now know that Norman is killing people while dressed as his mother, but he obviously knows that. With Identity, the doctors are aware that this man killed numerous people and has multiple personality disorder. We learn that at the end.
Then you have a twist that is a surprise to even the in-universe characters, where no one was aware of anything. Was The Sixth Sense this way? Did Bruce Willis know he was dead? I can't recall.
Then you have a twist that is a surprise to even the in-universe characters, where no one was aware of anything. Was The Sixth Sense this way? Did Bruce Willis know he was dead? I can't recall.