The large rectangular, grassy field has a flag placed at each corner to help the officials see when a ball goes "out of bounds". Chalk boundaries on the sides of the field are called touch lines; they may be from 100 to 130 yards long and spaced from 50 to 100 yards apart. The lines at each end of the field are called endlines (or goal lines). A ball passing over - not merely touching - any of these lines is ruled out of bounds.

Goals stand at the middle of each end line. Each goal is made up of two posts and a crossbar with a net attached, forming an opening 24 feet across and 8 feet high. A shot in which the ball passes beyond the goal line through the posts is scored as a "goal" (one point).

A large rectangular area extending in front of the goal defines the penalty area. Defending players are penalized if they commit certain infractions within this area. The goal area is a smaller rectangle inside of the penalty area. Players on the attack cannot come into contact with the goalkeeper in this area unless the goalie has the ball and both of his feet on the ground.

A center line divides the field in half and intersects the center spot inside the large center circle in the middle of the field.

A team goes on offense when it gains possession of the ball. It uses various formations, determined by the coach according to the situation. For example, when a team is ahead, its coach may insert extra defenders and employ a defensive formation. If his team is behind, he will frequently send in more offensive players, going with a formation that emphasizes attack. Other formations may center on a star player, with plays conceived to allow him to use his exceptional talents.

Three lines define a team's formation. The big scorers on a team are the forwards, who form the first (offensive) line. A forward line usually starts with five players: a center forward, left and right inside forwards, (these three are often known as strikers) and left and right outside forwards (also called wings or wingers). These players must be fast and shifty, and accurate at shooting and passing.

They exchange passes and dribble (move the ball along the ground with their feet) in crisscrossing patterns; they fake shots to draw defenders out of position; and they shoot when open. Forwards also drop back to break up the opposing team's attacks.

Three midfielders (also called halfbacks or linkmen) form the second line. A left, a center, and a right midfielder race up and down the field to unite their team's offense and defense.

Two defenders labeled fullbacks, seldom score but remain back in front of their team's goalkeeper as the last line of defense. The fullbacks' job is to take the ball from the opposition and pass it to a midfielder to initiate an attack. One fullback generally plays near the goal while his teammate (the sweeper) roams out to intercept passes.

This 5-3-2 formation (5 forwards, 3 midfielders, and 2 fullbacks) may shift to another configuration based on the need for either an offensive or defensive surge. For example, a 4-2-4 formation stresses a tight defense by using four defenders and a first line of only two strikers flanked by two wings. For greater offense, additional wings or inside forwards - or forward-moving midfielders - may promote more and better shots.

The goalkeeper (goalie or goal tender) generally remains near the goal he is defending. He must move quickly to steal crossing passes or to stop or tip away shots taken by the opposition. By rushing nearby ball handlers, he tries to cut down the angle at which they may shoot; moving closer to an opponent before he shoots the ball, a good goalie can either block the shot, or, more often than not, make the player shoot wide of the goal posts. The goalkeeper is the only player who may grasp or touch the ball with his hands and arms. When he controls the ball in this manner, he may elect to kick it far down field or throw it to a teammate in order to start an attack the other way.

International rules allow for only two substitutions per game, and a player who is pulled out cannot re-enter the match. (College coaches may substitute five players per game; high school rules allow unlimited replacement of players.)

One referee and two linesmen normally officiate the game. The referee keeps time and enforces the rules. Linesmen help watch for fouls, determine which team gets the ball when it goes out of bounds, and call "offside" infractions.

Pro soccer matches are divided into two 45-minute halves (termed "periods" in college). Depending on the abilities of the players, leagues are allowed to adjust the length of the halves. Only the referee may call time out to stop the clock (in most cases, only for an injury). The team winning a coin-toss chooses to either kick off or to defend a particular goal. A kickoff from the center spot begins play. With each team on its own side of the field, and with the defensive team outside the center circle, one offensive player softly kicks the ball forward to be retrieved by a teammate. All players are then free to move the ball with their feet as they advance it past the defense. Hard bodily contact is permitted only when attempting to kick the ball or hit it with the head. Near the opposing goal, the offensive players undertake to pull the defense out of position by faking and moving the ball quickly. By keeping players in motion, using crossing patterns, booting "centering" kicks, etc., the attackers hope to get a good shot on goal. If a shot bounces off the goal post or crossbar, or off another player, the ball is still considered in play and a goal may be scored on the rebound.

A ball that goes out of bounds is "out of play". Play is restarted by one of four methods:

1. A throw-in is required when the ball is knocked over a touch line (on the side of the field). An opposing player steps out of bounds and grasps the ball with both hands. Keeping both feet on the ground, he throws it in bounds to a teammate using an over-the-head motion.
2. A corner kick is awarded when a defensive player is last to touch a ball that crosses out of bounds over his own goal line. An offensive player boots the ball off of the ground from the nearest corner, and the other forwards and mid-fielders, positioned around the mouth of the goal, try to jump or race to kick or head the ball (strike it with the forehead) into the net.
3. A goal kick is given to the defense when an offensive player hits the ball out of bounds over the opponent's goal line. A formerly defensive player kicks the ball from the goal area out of the penalty area down field or to a member of his team.
4. A drop ball, where the ball is dropped by the referee between two opposite players, may also resume play when it is stopped for any reason.

When regulation game time expires, tied games go into an overtime period. A sudden death overtime may be used in which the first team to score wins the game. After the specified overtime, if teams are still tied they each take a series of tie-breaking "penalty shots" to decide the outcome.

A penalty kick (penalty shot), a direct free kick, or an indirect free kick is awarded to the opposing team for most fouls.

• Kicking (or attempting to kick) an opponent
• Obstructing (blocking an opponent's path)
• Tripping
• Rough pushing
• Bumping from behind
• Hitting
• Holding
• Touching the ball with the hands or arms

A direct free kick is awarded, from the point of the infraction when one of these eight fouls occurs outside the penalty area. Defenders may elect to line up shoulder-to-shoulder, no closer than ten yards away, to form a wall to block the free kick shot at their goal. After the kick, if no score was made, play resumes uninterrupted.

An indirect free kick must touch at least one other player before entering the goal. It is granted when an opposing player employs dangerous play (kicks the ball out of the goalie's hands, pushes a player without the ball, or strikes an opponent), exhibits unsportsmanlike conduct, or is offside. Offside is called when an attacker without the ball enters the opponent's half of the field before the ball does. There are four exceptions to this rule:

1. When two or more defenders are nearer their goal line than the offensive player;
2. When the offensive player moves between the ball and the goal line after a teammate kicks the ball;
3. When the ball was last touched by a defensive player: and
4. When the offensive player receives the ball from a throw-in, corner kick, goal kick, or drop ball.

For excessive or dangerous fouling, the referee may take out and flash a yellow card as a warning to the player. For subsequent fouls by the same player, the referee may choose to bring out a red card, meaning the player is ejected from the game with no substitution allowed.