A jury is a group that decides a contest or a court case together. If you get summoned for jury duty and get picked as one of the 12 members of the jury, you’ll help decide if someone is guilty or not.
A jury is any group that makes a group decision. In the County Fair, the stakes aren't so high — just respect for your baking skills or pig-raising talents. But many juries are convened by courts to decide whether someone is innocent or guilty. In this case, the jury is sworn to act according to the law. Jury comes from the Old French word for "oath," pointing to the promise to deliver the truth that a jury swears to.