Cornerback

An example of an offensive and a defensive alignment. The offense has two wide receivers one on each side of the formation. The defense has two cornerbacks, each opposite one of the wide receivers.
Cornerbacks across from their assigned receivers in a base 3–4 defense

A cornerback (CB) is a member of the defensive backfield or secondary in gridiron football.[1] Cornerbacks cover receivers most of the time, but also blitz and defend against such offensive running plays as sweeps and reverses. They create turnovers through hard tackles, interceptions, and deflecting forward passes.

Other members of the defensive backfield include strong and free safeties.

The cornerback position requires speed, agility, strength, and the ability to make rapid sharp turns. A cornerback's skill set typically requires proficiency in anticipating the quarterback, backpedaling, executing single and zone coverage, disrupting pass routes, block shedding, and tackling. Cornerbacks are among the fastest players on the field. Because of this, they are frequently used as return specialists on punts or kickoffs.