A position on the offense responsible for initiating the majority of offensive plays. The quarterback is relaying the play call to the rest of the offense, adjusting the offense prior to the snap, taking the snap from center, and executing the play. That can entail handing the ball off to a running back, running the ball on their own, or attempting a pass downfield. Quarterbacks must have the capacity to analyze the defense, and should have a strong, accurate arm for downfield passes.
The quarterback is the leader of an offense. Teams rely on a quarterback to execute plays as efficiently as possible. A quarterback has to be able to line his team up and evaluate the defense quickly, making any adjustments necessary to try and maximize the offense's success. This can mean changing a play at the line of scrimmage, which is called an "audible". The quarterback is almost always responsible for attempting passes downfield, and must do so while avoiding the defensive pass rush. An effective quarterback will commit very few turnovers and have a high completion percentage.