What does "PAT" stand for?

What position did Aaron Donald play? What is the role of a "long snapper"? What is a "Hail Mary" pass? What is "the red zone" in football? What is a "two-minute warning"? What do referees throw to signal a penalty? What do officials throw to mark a spot, such as a fumble or punt catch point? What color flag does an NFL coach throw to challenge a play?