The baseline in basketball is the boundary line running along the edges of the court on the sides behind the baskets. It marks where a player or the ball goes out of bounds, and is used to separate the area of play and the area that is out of bounds. On a typical basketball court, the baseline will measure 50 feet long, however the length can vary by court. The baseline can also be referred to as the end line.
Everytime a basket is scored, a player on the non-scoring team must step out of bounds behind the baseline and pass the ball to a teammate. It is also used as the boundary for inbounding the ball after a timeout or simply after the ball goes out of bounds. The baseline is usually a common point of reference on replays, as officials can see whether any part of the player's body or the ball is touching the baseline, making them out of bounds.