Player Positions in American Football

When two opposing American football teams meet on the gridiron (playing field), the player positions depend on whether the football team is playing offense or defense. Football pits the offense, the team with the ball, against the defense, which tries to prevent the offense from scoring. Each side lines up facing the other with the football in the middle.
The players on the offensive side of the ball include the
Quarterback: The leader of the team. He calls the plays in the huddle, yells the signals at the line of scrimmage, and receives the ball from the center. Then he hands off the ball to a running back, throws it to a receiver, or runs with it.
Center: The player who snaps the ball to the quarterback. He handles the ball on every play.
Running back: A player who runs with the football. Running backs are also referred to as tailbacks, halfbacks, and rushers.
Fullback: A player who's responsible for blocking for the running back and also for pass-blocking to protect the quarterback. Fullbacks, who are generally bigger than running backs, are short-yardage runners.
Wide receiver: A player who uses his speed and quickness to elude defenders and catch the football. Teams use as many as two to four wide receivers on every play.
Tight end: A player who serves as a receiver and also as a blocker. This player lines up beside the offensive tackle to the right or the left of the quarterback.
Left guard and right guard: The inner two members of the offensive line, whose jobs are to block for and protect the quarterback and ball carriers.
Left tackle and right tackle: The outer two members of the offensive line.
The players on the defensive side of the ball include the
Defensive tackle: The inner two members of the defensive line, whose jobs are to maintain their positions in order to stop a running play or run through a gap in the offensive line to pressure the quarterback or disrupt the backfield formation.
Defensive end: The outer two members of the defensive line. Generally, their jobs are to overcome offensive blocking and meet in the backfield, where they combine to tackle the quarterback or ball carrier. On running plays to the outside, they're responsible for forcing the ball carrier either out of bounds or toward (into) the pursuit of their defensive teammates.
Linebacker: These players line up behind the defensive linemen and generally are regarded as the team's best tacklers. Depending on the formation, most teams employ either three or four linebackers on every play. Linebackers often have the dual role of defending the run and the pass.
Safety: The players who line up the deepest in the secondary — the last line of defense. There are free safeties and strong safeties, and they must defend the deep pass and the run.
Cornerback: The players who line up on the wide parts of the field, generally opposite the offensive receivers.

By Howie Long and John Czarnecki