Basketball is a team sport, the objective being to shoot a ball through a basket horizontally positioned to score points while following a set of rules. Usually, two teams of five players play on a marked rectangular court with a basket at each width end. Basketball is one of the world's most popular and widely viewed sports. A regulation basketball hoop consists of a rim 18 inches (46 cm) in diameter and 10 feet (3.0 m) high mounted to a backboard. A team can score a field goal by shooting the ball through the basket during regular play. A field goal scores two points for the shooting team if a player is touching or closer to the basket than the three-point line, and three points (known commonly as a 3 pointer or three) if the player is behind the three-point line. The team with the most points at the end of the game wins, but additional time (overtime) may be issued when the game ends with a draw. The ball can be advanced on the court by bouncing it while walking or running (dribbling) or throwing (passing) it to a team mate. It is a violation to move without dribbling the ball (travelling), to carry it, or to hold the ball with both hands then resume dribbling (double dribble). Various violations are generally called "fouls". Disruptive physical contact (a personal foul) is penalized, and a free throw is usually awarded to an offensive player if he is fouled while shooting the ball. A technical foul may also be issued when certain infractions occur, most commonly for unsportsmanlike conduct on the part of a player or coach. A technical foul gives the opposing team a free throw, and the opposing team is also retained possession of the ball. Basketball has evolved many commonly used techniques of shooting, passing, dribbling, and rebounding, as well as specialized player positions and offensive and defensive structures (player positioning) and techniques. Typically, the tallest members of a team will play "center", "power forward" or "small forward" positions, while shorter players or those who possess the best ball handling skills and speed play "point guard" or "shooting guard". Competitive basketball is primarily an indoor sport played on a carefully marked and maintained basketball court.
Games are played in four quarters of 10 (FIBA)or 12 minutes (NBA). College games use two 20-minute halves,while high school varsity games use 8 minute quarters.15 minutes are allowed for a half-time break under FIBA, NBA, and NCAA rules and 10 minutes in high school. Overtime periods are five minutes in length except for high school which is four minutes in length. Teams exchange baskets for the second half. The time allowed is actual playing time; the clock is stopped while the play is not active. Therefore, games generally take much longer to complete than the allotted game time, typically about two hours. Five players from each team may be on the court at one time.Substitutions are unlimited but can only be done when play is stopped. Teams also have a coach, who oversees the development and strategies of the team, and other team personnel such as assistant coaches, managers, statisticians, doctors and trainers. For both men's and women's teams, a standard uniform consists of a pair of shorts and a jersey with a clearly visible number, unique within the team, printed on both the front and back. Players wear high-top sneakers that provide extra ankle support. A limited number of time-outs, clock stoppages requested by a coach (or sometimes mandated in the NBA) for a short meeting with the players, are allowed. They generally last no longer than one minute. The game is controlled by the officials consisting of the referee, one or two umpires and the table officials.Usually there are a total of three referees on the court. The table officials keep track of each teams scoring, timekeeping, individual and team fouls, player substitutions, team possession arrow, and the shot clock.