The quarterback is a player on the offense who is the team's most valuable player. The quarterback starts with the ball on every play and can choose to pass the ball, hand it off to a running back, or run with it himself for a quarterback sneak.
After the snap, the quarterback can:
On a passing play the quarterback scans the field for an open receiver and then throws the ball to the receiver. It's a completion if the pass is caught. The pass is incomplete if the ball is dropped or thrown out of bounds.
The pocket is an area on the field created by the offensive line to protect the quarterback from being sacked. The pocket gives quarterbacks time to scan the field to find an open receiver to pass to.
On a running play the quarterback hands the ball to a running back to run with. This is called a hand off.
The quarterback sneak is a play where the quarterback takes the ball and runs with it on the field. On a QB sneak the quarterback will run towards the sidelines. Quarterback sneaks can be planned or happen if a player on the defense breaks through the pocket. In the second case, the quarterback is trying to avoid a sack. Quarterback sneaks are risky plays since the quarterback is at risk of being tackled and injured.
Being a good quarterback at any level is tough. The position requires you to have exceptional abilities throwing the ball as well as have a great understanding of opposing defenses and your own playbook. Here are a few traits that are important in being good quarterback:
Being a good quarterback is not just about how far or fast you can throw the football. In fact, most quarterbacks who don't tend to have success on the field is because of their lack of preparation on the mental side of the game. Those who practice, watch film, and learn the ins and outs of football are the ones who tend to have great success on the field.