Basketball is a competitive sport invented as a men's game in 1891 by James Naismith in Springfield, Massachusetts but now played on every inhabited continent and by men and women, most often contested by two teams, each comprising five participating players, for whom substitutions may be made. For some teams the substitutions may only consist of a few players and for others they may have anywhere from 7 to 8 subs. The team attempts to advance a spherical ball through a cast-iron basket with attached net and backboard, elevated such that the basket rim is–in most professional leagues–ten feet (3.048 meters) from the surface of the rectangular basketball court, for indoor games usually made of hardwood and for outdoor games usually made of asphalt, on which the sport is played.
Offensively, a player advances the ball either by bouncing it himself while stationary or moving (dribbling) or by throwing it (passing) it to a teammate, such that a player, within the time permitted by a shot clock, eventually propels (shoots) the ball toward the basket; should the ball pass through the basket, one (free throw), two (field goal), or three (three-point field goal) points, depending on the distance from which the shot is taken, are awarded; the player, in most cases, to have tendered the ball to the scoring player is credited with an assist. Several strategies are employed by a team toward the end of generating uncontested shots for players, who most often begin a given play in distinct areas—the center and power forward proximate to the basket (top of the key); the small forward and shooting guard proximate to the three-point arc; and the point guard passim. The team to have scored more points upon the expiration of the time allotted for the game, usually between 40 and 60 minutes and divided into four equal quarters or two equal halves, is the winner, and ties are most often settled during overtime periods.
A defense attempts to prevent an offensive team from scoring and to garner the ball for itself, employing various strategies to force an opposing player to surrender (turnover) the basketball, by dispossessing (steal) a player or successfully contesting his shot (block) or, upon an opponent's making an unsuccessful shot, overcoming an opponent to win the loose ball (rebound).
Certain disruptive contact, especially that by which an advantage is gained, is penalized (as a personal foul), as is unsportsmanlike conduct (as a technical foul), with disqualification often imposed on players who accumulate a pre-arranged number of fouls in one game. Certain means of ballhandling, such as one's running with the ball while not dribbling (travelling) or one's catching the ball between dribbles (double dribbling) are proscribed and, when committed by a given team, result in the awarding of possession to the opposing team.