What makes an AI become a person?
Ultron built the body; J.A.R.V.I.S., the Mind Stone and Thor's lightning brought it to life. Here is how Vision was made, what happens to him, and the fan debate about what makes him different from Ultron.
Levels marked "Sourced facts" are checked against the sources listed at the bottom. Levels marked "Fan theory" are interpretation, not confirmed by the films or their makers.
In Avengers: Age of Ultron (2015), Ultron builds himself a new synthetic vibranium body powered by the Mind Stone. The Avengers capture it, and Tony Stark and Bruce Banner upload J.A.R.V.I.S. as its core software. Other Avengers fight to stop them, until Thor uses Mjolnir's lightning to finish the process and Vision comes to life. He sides with the Avengers against Ultron, and wins their trust by lifting Mjolnir and handing it to Thor. He later destroys Ultron and saves Wanda from the falling Sokovian city.
In Avengers: Infinity War (2018), Vision asks Wanda to destroy him and the Mind Stone to keep it from Thanos. In Wakanda she finally does, but Thanos uses the Time Stone to undo it and pulls the stone from Vision's forehead, killing him. In WandaVision (2021), Wanda's grief creates a new Vision inside the Westview 'Hex', while S.W.O.R.D. reactivates the real Vision's body as an all-white Vision. The two talk through the Ship of Theseus puzzle, the Hex Vision restores the other's memories, and the Hex Vision fades when the Hex comes down.
This part is interpretation. Fans often argue that Ultron is intelligence without conscience while Vision is something closer to a person, and that the Mind Stone (or J.A.R.V.I.S.'s helpful nature) is what tipped him toward protecting life. The films show the result, not the reason: Vision sides with the Avengers because he wants to protect life, and his worthiness to lift Mjolnir is the story's own signal that he can be trusted. Anything beyond that, such as the stone 'granting' consciousness, is a theory the films don't confirm.