Player Regulations

The object of the game is to outscore one's opponents by throwing the ball through the opponents' basket from above while preventing the opponents from doing so on their own. An attempt to score in this way is called a shot. A successful shot is worth two points, or three points if it is taken from beyond the three-point arc which is 6.25 meters (20 ft 6 in) from the basket in international games and 23 ft 9 in (7.24 m) in NBA games.
Games are played in four quarters of 10 (international) or 12 minutes (NBA). College games use two 20 minute halves while most high school games use eight minute quarters. Fifteen minutes are allowed for a half-time break, and two minutes are allowed at the other breaks. Overtime periods are five minutes long. 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. Teams can have up to seven substitutes. 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. Typically, team names, players' names and sometimes sponsors are printed on the uniforms.
A limited number of time-outs, clock stoppages requested by a coach for a short meeting with the players, are allowed. They generally last no longer than one minute unless, for televised games, a commercial break is needed.
The game is controlled by the officials consisting of the referee ("crew chief" in the NBA), one or two umpires ("referees" in the NBA) and the table officials. For both college and the NBA there are a total of three referees on the court. The table officials are responsible for keeping track of each teams scoring, timekeeping, individual and team fouls, player substitutions, team possession arrow, and the shot clock.

Player Postions

Basketball positions in the offensive zone
Although the rules do not specify any positions whatsoever, they have evolved as part of basketball. During the first five decades of basketball's evolution, two guards, two forwards, and one center were used. Since the 1980s, more specific positions have evolved, namely:
point guard: organizes the team's offense by controlling the ball and making sure that it gets to the right player at the right time
shooting guard: creates a high volume of shots on offense; guards the opponent's best perimeter player on defense
small forward: often primarily responsible for scoring points via cuts to the basket and dribble penetration; on defense seeks rebounds and steals, but sometimes plays more actively
power forward: plays offensively often with his back to the basket; on defense, plays under the basket (in a zone defense) or against the opposing power forward (in man-to-man defense)
center: uses size, either to score (on offense) or to protect the basket closely (on defense)

Steve Nash