A defensive player who generally lines up slightly behind the line of scrimmage, differing from defensive linemen and linebackers who generally line up on the line of scrimmage. There are two main specialized defensive back positions: the safety and the cornerback.
Also known as the "secondary".
Defensive backs will often line up against wide receivers to protect against passing plays or move in on running plays and prevent extended rushing gains. Defensive backs will also line up against tight ends and running backs who are lined up away from behind the quarterback.