The long jump is a track and field event in which athletes combine speed, strength, and agility in an attempt to leap as far as possible from a take off point. This event has been an Olympic medal event since the first modern Olympics in 1896 and has a history in the ancient Olympics.
At the elite level, competitors run down a runway (usually coated with the same rubberized surface as running tracks, crumb rubber also vulcanized rubber) and jump as far as they can from a wooden board 20 cm/8 inches wide that is built flush with the runway into a pit filled with finely ground gravel or sand. If the competitor starts the leap with any part of the foot past the foul line, the jump is declared a foul and no distance is recorded. A layer of plasticine is placed immediately after the board to detect this occurrence. An official (similar to a referee) will also watch the jump and make the determination. The competitor can initiate the jump from any point behind the foul line; however, the distance measured will always be perpendicular to the foul line to the nearest break in the sand caused by any part of the body or uniform. Therefore, it is in the best interest of the competitor to get as close to the foul line as possible. Competitors are allowed to place two marks along the side of the runway in order to assist them to jump accurately. At lesser meet and facilities, the plasticine will likely not exist, the runway might be a different surface or jumpers may initiate their jump from a painted or taped mark on the runway.
Each competitor has a set number of attempts. That would normally be three trials, with three additional jumps being awarded to the best 8 or 9 (depending on the number of lanes on the track at that facility, so the event is equatable to track events) competitors. All legal marks will be recorded but only the longest legal jump counts towards the results. The competitor with the longest legal jump (from either the trial or final rounds) at the end of competition is declared the winner. In the event of an exact tie, then comparing the next best jumps of the tied competitors will be used to determine place. In a large, multi-day elite (like the Olympics or World Championships) competition, a set number of competitors will advance to the final round, determined in advance by the meet management. A set of 3 trial round jumps will be held in order to select those finalists. It is standard practice to allow at a minimum, one more competitor than the number of scoring positions to return to the final round, though 12 plus ties and automatic qualifying distances are also potential factors.
Reference: Wikipedia Long Jump