What is the job of a Jury?

they decide if you go to jail or not given the evidence

Added: (in a criminal trial) the jury hears the case presented by both the prosecution and the defense and relying on the instructions given them on the law by the judge, and their own good judgement, they decide on the fate of the defendant. (in a civil trial) they perform the same function except the principals are known as the Plaintiff and the Respondent, and the jury hears evidence that will influence them in their decision to render a verdict for the side having the greater weight of convincing evidence.