Free throw lane

The key, officially referred to as the free throw lane by the National Basketball Association (NBA) and the National Collegiate Athletic Association (NCAA), the restricted area by the international governing body FIBA, and colloquially as the lane or the paint, is an area on a basketball court underneath the basket bounded by the endline, the free-throw line and other lines which are known as freebody lines, that are usually painted (although unpainted on some courts with painted perimeters). It is a critical area on the court where much of the action takes place in a game.

The key, in all games, starting with FIBA's amendments to its rules in 2010 (to be first implemented after the 2010 FIBA World Championship), is rectangular. Prior to 2006, the key in FIBA-sanctioned tournaments (mostly basketball played outside the United States, and almost all international tournaments including the World Championships and the Olympics) was trapezoidal in shape. Both NBA and FIBA keys are 16 feet (4.9 m) wide, while NCAA keys are narrower at 12 feet (3.7 m).

The most-commonly enforced rule on the key is the "three seconds rule" in which a player from the offensive team is prohibited from staying on the key for more than three seconds, or else the player's team will lose possession of the ball. Another rule enforced is the lane violation in which players from both teams are prohibited to enter the lane until after the free throw shooter releases the ball from his hands (the shooter is prohibited to enter the key until after the ball hits the rim). An innovation is the introduction of the restricted area arc directly underneath the basket where the defending player cannot force an offensive foul on the opposing player.

Each level of play has different specifications for the size and shape of the key: in American leagues, where the basketball court is measured in imperial units, the shape is rectangular, while in FIBA-sanctioned events, which use the metric system, the shape was trapezoidal, before being changed to a rectangle as well. In addition to the bounding rectangle, the key includes a free-throw circle at its "head" or "top".

...
Wikipedia