(1) What is an offside position?
A player is in an offside position if he does not have two players, usually a goalkeeper and a defender, between himself and the goal.
This means he must stay in front of or level with the last defender of the opposition team.
However, being in an offside position in itself is not an offence.
(2) How can a player be offside?
A player breaks the offside law when he is in an offside position when a pass is played to him.
It means a striker might appear to be offside when the ball reaches him but in fact he was onside when it was played.
FIFA recently amended the law to clarify that an offside player who is not 'actively involved in play' is not committing an offence as long as he is not interfering with play in an attempt to encourage attacking football.
"Interfering with play means playing or touching the ball passed or touched by a team-mate," the law says.
A player could still be offside though if the referee think he is interfering with an opponent, such as blocking a goalkeeper's view, or has gained an advantage.
(3) A player cannot be adjudged offside if…
The ball has come from a goal kick, throw-in or a corner
The player is in his own half when the pass is played
The player is level with or behind the ball when the pass is played
The player is not actively involved with play
(4) How is offside punished?
If a player receives the ball in an offside position, the referee awards a free-kick where the ball was touched.