Gridiron football Gridiron football ( or simply football ) , sometimes known as North American football , is an umbrella term for related codes of football primarily played in the United States and Canada . The predominant forms of gridiron football are American football and Canadian football . The terms refer to the sport ' s characteristic playing field , which is marked with a series of parallel lines resembling a gridiron . " Gridiron " football developed in the late 19th century out of the older games related to the games now known as rugby football and association football . It is distinguished from other football codes by its use of helmets and shoulder pads , the forward pass , the system of downs , a line of scrimmage , more specialist positions and formations , free substitution , platooning — the use of different players for offense and defense , measurements in yard s , and the ability to score points while not in possession of the ball by way of the safety . Walter Camp is credited with creating many of the rules that differentiate gridiron football from its older counterparts . The international governing body for all forms of gridiron football is the International Federation of American Football ( IFAF ) . Terminology . The term " gridiron " in reference to football first developed in Canada . It originally referred to the sport ' s playing field , alternately known as the " grid " , due to the its patterned markings which give it the appearance of a gridiron . The terms " gridiron " and " grid " were thence applied loosely to the game itself . Especially outside of the U . S . and Canada , the terms " gridiron " and " gridiron football " are often used to distinguish the North American sport from other codes of football . " Gridiron " is particularly common in Australia and New Zealand . In some cases the terms are used specifically for American football , sometimes even in distinction from Canadian football , though it is now often used as a blanket term for all North American variants . Play of the game . This is a minimal description of the game in general , with elements common to all or almost all variants of the game . For more specific rules , see each code ' s individual articles . Prior to the start of a game , a coin toss determines which team will kick off the ball to their opponent . Each team lines up on opposite halves of the field , with a minimum ten yards of space between them for the kickoff . At this point , play from scrimmage begins . The team in possession of the ball is on " offense " and the opponent is on " defense " . At least half of the players ( the exact number varies by code ) on the offense must line up on the line of scrimmage , including the snapper , who handles the ball before play commences ; the rest must line up behind the line . Neither the offense nor the defense can cross the line of scrimmage before the play commences . Once the offense sets in formation , the snapper snaps the ball to one of the players behind him . The play has now commenced , and the offense ' s goal is to continue advancing the ball toward their opponent ' s end zone . This can be done either by running with the ball or by a rule unique to gridiron football known as the " forward pass " . In a forward pass , a player from behind the line of scrimmage throws the ball to an eligible receiver ( another back or one player on each end of the line ) , who must catch the ball before it touches the ground . The play stops when a player with the ball is tackled to the ground , runs out of the boundaries of the field , or a forward pass hits the ground without being caught . In order to keep play moving , the offense must make a certain amount of progress ( 10 yards in most leagues ) within a certain number ( 3 in Canada , 4 in the United States ) of plays , or downs . If the offense does indeed make this progress , a " first down " is achieved , and the team gets 3 or 4 more plays to achieve another 10 yards . If not , the offense loses possession to their opponent at the spot where the ball is . More commonly , however , the team on offense will , if they have a minimal chance of gaining a first down and have only one play left to do it ( " fourth down " in the U . S . , " third down " in Canada ) , attempt a " scrimmage kick " . There are two types of scrimmage kick : a punt is when the ball is kicked downfield as far as possible ; the kicking team loses possession of the ball after the kick and the receiving team can attempt to advance the ball . The other scrimmage kick is a field goal attempt . This must be attempted by place kick or ( more rarely ) drop kick , and if they pass through the goal set at the edge of the opponent ' s end zone , the team scores three points ( four in rare variants and special circumstances ) . If the team in possession of the ball , at any time , advances the ball into the end zone , it is a touchdown , and the team scores six points and a free play known as a try . In a try , a team attempts to score one or two points ( rules vary by each league , but a field goal on a try is usually worth one point while another touchdown is worth two ) . If the player with the ball is tackled while he is in his own end zone , the defense scores a safety , worth two points . After a try , safety or field goal , the team that had possession of the ball goes back to the middle of the field and kicks the ball off to their opponent , and play continues as it did in the beginning of the game . Play continues until halftime . ( Each team switches sides of the field with each other halfway through each half , at the end of a quarter . ) After the halftime break , the team that did not kick off at the beginning of the game kicks off . Whichever team has more points at the end of the game is declared the winner ; in the event of a tie , each league has its own rules for overtime to break the tie . Origin of the gridiron . According to the early rules of American football , fields were marked in a checkerboard pattern of grids . The ball would be snapped in the grid in which it was downed on the previous play . This system was abandoned in favor of the system of yard lines and hash marks now used and brought the gridiron design more in line with Canadian football . As described in " Outdoor Sports and Games " ( 1911 ) : " A football field is 330 feet long by 160 feet wide . At each end are goal posts set 18 feet 6 inches apart , with a crossbar 10 feet above the ground . The field is marked off in chalk lines similar to a tennis court , these lines being 5 yards apart . The centre of the field where the play starts is 55 yards from either end . It is usually customary to run lines parallel to the sides of the field , also 5 yards apart , but as a field is but 160 feet wide the first and last of these lines are but 5 feet from the side lines instead of 5 yards . The lines on a football field make a checkerboard effect and have given to the field the name of " gridiron . " " An example of a field that was marked in the original gridiron pattern was the old Archbold Stadium at Syracuse University , which has since been torn down . Usage . The word " gridiron " alone can refer either to the field or to the sport . In North America , however , it is mostly used in reference to the field , usually in a somewhat figurative or poetic sense ( e . g . " the players are getting set to battle it out on the gridiron " . ) In some other English - speaking countries — particularly Australia and New Zealand — it is the primary term used to refer to the sport , differentiating it from other forms of football such as Australian football , association football , rugby league , and rugby union . In British parlance the most frequently used term is " American football " , but " gridiron " is also used to describe the game .