Here are some explanations of three frequently misunderstood rules:
Ball In/Out of Play (Law 9):
The ball is out of play when:
- it has wholly crossed the goal line or touch line whether on the ground or in the air
- play has been stopped by the referee
The ball is in play at all other times, including when:
- it rebounds off a goalpost, crossbar or corner flagpost and remains in the field of play
- it rebounds off either the referee or an assistant referee when they are on the field of play
This is sometimes confusing because there are two major differences from other popular sports.
First, in sports such as American football and basketball the line is itself out of bounds. So if a player touching the ball, or the ball itself, touches the line, then the ball is out. Not so in soccer. The line is in play, the line is in bounds, the line is part of the field.
The whole ball must be outside the whole line for it to be out of play. Even if the part of the ball touching the ground is outside the line, as long as some part of the ball still extends above the line the ball is still in play.
Second, in American football and basketball being in play is partly a question of the position of the player, not just the ball. So if a basketball or football player steps on or outside the lines while touching the ball, even if the ball is inside the lines, out of bounds is called. Conversely, even if the ball is outside the lines but has not hit the ground yet, it can be played (caught for a reception or deflected to a team mate) by a player as long as the player has a foot or feet in bounds. In basketball as long as a player deflects the ball before touching the floor out of bounds, the ball is still in play.
In soccer it is all about the position of the ball, whether or not the player is inside, on, or outside the line. So even though a player might keep one foot inside the line while playing a ball that is in the air but wholly outside the line, that ball is out of play--even if it never touches the ground out of play. Conversely, even though a player might have a foot outside the line while playing a ball that is inside, on, or above the line, that ball is still in play.
This can be very important with respect to the goalkeeper. The GK can handle the ball as long as the ball is inside the penalty area, and the lines are part of the penalty area. Even if the GK is standing inside her goal, as long as she keeps the ball in play with extended arms (as long as the whole ball is not over the whole line) no goal is scored. Or imagine a GK who has slid so that most of her body is on the ground outside the lines--as long as she keeps the ball inside the lines she is making a legal play (not handling the ball outside the penalty area, or not letting it go out of play).
This is relevant to when a goal is scored (Law 10):
"A goal is scored when the whole of the ball passes over the goal line, between the goalposts and under the crossbar, provided that no infringement of the Laws of the Game has been committed previously by the team scoring the goal."
Offside Offense (Law 11):
A great visual explanation of the offside offense is here (I
highly recommend this for parents, coaches, and players--it is even better than FIFA's video explanation):
http://www.dynamic-thought.com/OffsideClickette.html
Here is the explanation:
A player is in an OFFSIDE POSITION if all of the following are true:
The player is...
- In the opponent's half of the field, AND
- Nearer the opponent's goal line than the ball, AND
- Nearer the opponent's goal line than the second to last opponent
The 'nearer' judgement involves any part of the head, body, or feet, being nearer the goal line, but NOT the arms alone. The 'second to last opponent' is typically determined by the goal keeper and one defender. It is entirely possible, however (e.g., during or just after a corner kick), that the GK has come out quite far and the second to last defender is determined by two defenders.
Being in an offside position is not itself an offense.
An OFFSIDE OFFENSE is committed by a player if and only if:
At the moment the ball is touched or played by a team mate*
- The player is in an offside position, AND
- The referee judges the player is involved in active play** by interfering with play, interfering with an opponent, or gaining an advantage by being in that position (not restricted to the obvious case of receiving the pass and continuing the attack)
* This is one condition that usually confuses spectators. They will see a forward run past the second to last defender and receive the ball in empty space between that defender and the goal keeper, and screams of "offsides!"*** ensue. But if the forward timed her run correctly and didn't run past the defender until after the ball was passed, then she did not commit an offside offense, even if she gets behind the defense before the ball--this is good play by the forward and the passer, not so much by the defense.
** This is another condition that confuses people. First, it is possible for one or more players to be in a offside position without being involved in active play, in which case they are not committing an offside offense. The video linked above illustrates one such scenario. Second, spectators often complain that the Assistant Referee's flag "came up very late". But the AR is supposed to judge offside position when the ball is played and then wait to determine if any player in offside position takes part in active play. Sometimes this looks to the spectator as if the AR is making some sort of mistake or inappropriately delaying the call.
*** There is no such thing as 'offsides' in soccer. The correct terminology is 'offside'. I would not recommend pointing this out to anyone in the heat of the moment however...