Offensive Lineman In American football , each team has eleven players on the field at one time . Because the rules allow unlimited substitution between plays , the types of players on the field for each team differ depending on the situation . At the college and National Football League levels , most play only offense or only defense , with " two - way " players being a thing of the past . Offense . The offensive team or offense in football is the team that begins a play from scrimmage in possession of the ball . A play usually begins when the quarterback takes a snap from the center and then either hands off to a running back or a receiver , passes to a receiver or a running back , runs the ball himself , spike s the ball or takes a knee . Also , the center may snap the ball directly to a running back or receiver , usually from a Wildcat formation , where a running back or receiver takes the place of the quarterback in a shotgun formation . The purpose of the spiking the ball is to stop the game clock if the offense is running out of time . The purpose of taking a knee is to allow the clock to run with minimal risk of turning the ball over . If a player runs the ball and stays in bounds , or if a player receives a pass and stays in bounds ( this has the same effect as taking a knee ) , then the clock keeps ticking . But if a player running the ball goes out of bounds , or there is an incomplete pass , then the clock stops . The goal of the offensive team is to earn points for the entire team . The offensive earns points by scoring a touchdown . A touchdown results in 6 points . After the offense scores a touchdown , the special teams comes onto the field to attempt an extra point . An extra point results in 1 point ( kicking ) or 2 points ( run or pass ) . The offensive team , however , can also help the team score by getting good field position for an attempt at a field goal . A field goal earns the team 3 points . The offensive unit in football consists of a quarterback , linemen , running backs , tight ends , and wide receivers . The function of most of the linemen is to block . The offensive line consists of a center , two guards , two tackles and one or two tight ends . Backs include running backs who frequently carry the ball and receive swing passes and screens , and a fullback , who usually blocks , and occasionally carries the ball or receives a pass . The primary function of the wide receiver s is to catch passes . The makeup of the offense and how it operates is governed by the head coach or offensive coordinator ' s offensive philosophy . Teams can vary the number of wide receivers , tight ends and running backs on the field at one time . Football rules limit the flexibility of offensive formations . Seven players must line up on the line of scrimmage , and only the two at the end are eligible to catch passes . Sometimes , offensive lineman can declare eligibility and become " tackle eligible . " Jumbo Elliott and Dan Klecko are two tackles who have caught touchdowns while being tackle eligible . Typical formations include : Defense . The defensive team or defense is the team that begins a play from scrimmage not in possession of the ball . The object of the defensive team is to prevent the other team from scoring . Unlike many sports , defense in American football can be very aggressive , seeking to attack the opposing quarterback and to push the offense back from the line of scrimmage . The sign that the defensive goal has been accomplished is recovering possession of the football before the offensive team scores , which usually involves the offensive team punting the ball on fourth down . Other possibilities include having the ball turned over on downs , getting an interception or recovering a fumble . Also , if an offense advances down - field and into the " red zone " ( within the 20 - yard line of the defense ) and is threatening to score a touchdown , the defense can consider its goal accomplished if it forces the offense to settle for a field goal ( three points ) rather than a touchdown ( six points ) . Many teams operate specific defensive plays for the so called ' Red Zone ' specifically to achieve this . Unlike the offensive team , there are no formally defined defensive positions . A defensive player may line up anywhere on his side of the line of scrimmage and perform any legal action . Most sets used in football , however , include a line composed of defensive ends and defensive tackles and ( behind the line ) linebackers , cornerbacks , and safeties . Defensive ends and tackles are collectively called defensive linemen , while the cornerbacks and safeties are collectively called defensive backs , or the secondary . Defensive back — It is not a specific position ; however , it is any position besides the line , including cornerbacks , safeties , etc . , that is behind the line of scrimmage . Typical defensive formations include : Special teams . Special teams are units that are on the field during specific situations . They include a kickoff team , a kick return team , a punting team , a punt blocking and return team , a field goal and extra point team , a field goal blocking team and " hands team " used for onside kick s to prevent the kicking team from recovering a kick , usually by recovering the ball themselves . Though fewer points are scored on special teams than on offense , special teams play determines where the offense will begin each drive , and thus it has a dramatic impact on how easy or difficult it is for the offense to score . Because these aspects of the game can be so different from general offensive and defensive play , a specific group of players is drilled in executing them . Most special teams players are second - and third - string players from other positions , but there are also specialized players on these teams , including :