Linebackers typically line up about three to five yards behind the line of scrimmage. Their main role is to stop the offensive team members from gaining any yards down the field. The linebackers are the players responsible for stopping the ball and ball carrier. The linebacker provides extra run and pass protection.
The linebacker is often considered to be the most important defensive position on the field at any given time. This is due to their versatility and responsibilities of stepping in where help is needed. Just like the free safety, the linebacker's course of action is determined after each snap and is very different each time.
The defensive backfield is located just behind the line of scrimmage. Linebackers stand in the defensive backfield, which is usually half of the football field.
A 3-4 defense is another type of formation in football where the defense consists of three defensive linemen and four linebackers.