scrimmage: offense
The offense or team with ball possession has four downs to gain 10 yards. If it succeeds, it is given another four downs; if not, the ball is turned over to the other team by means of a punt.
right tackle 
Position on the outside of the right guard; this player blocks the opposing defense and protects the quarterback in passing situations.
right guard 
Position to the right of the center; this player has a blocking role in passing and running situations.
center 
Position at the center of the offensive line; this player puts the ball in play by snapping it to the quarterback.
left tackle 
Position on the outside of the left guard; this player blocks the opposing defense and especially protects the quarterback in passing situations.
left guard 
Position to the left of the center; this player has a blocking role on passing and running plays.
quarterback 
Position behind the center; the offensive leader, this player gathers teammates together between downs and communicates tactics.
fullback 
Position behind the quarterback; this player protects the quarterback in passing situations and blocks for the tailback.
tailback 
Position behind the fullback; this fast player often carries the ball (running play).
tight end 
Position on the outside of the tackle; this versatile player blocks opposing players and catches passes.
wide receiver 
Two positions at the far end of the offensive line; they use speed and agility to separate themselves from the defense and catch passes.
line of scrimmage 
Imaginary line along which the offense and defense face one another before the ball is snapped.