[kevkrom]

I suppose I should add, if a player is in an offside position, but he is not involved in the play, that player is not supposed to be ruled offside, which is a relatively modern change to the rule, IIRC. It’s also a judgement call as to what “involved in the play” means - I’ve seen a goal disallowed when a player was in an offside position, didn’t touch the ball, didn’t screen the defender or keeper, but was judged to be “distracting” to the keeper by being in his peripheral vision. (I disagreed with the call, but it does show the subjective nature of it.)

[cartan]

Your explanation is very good. Most people erroneously believe that one of the two defenders has to be the goalie, for example. Also, many people do not know that it is never offside when you pass the ball to someone behind you.

Another thing that few people know is that it is ok (not offside) if one or both of the defenders are even outside the field, behind the goal line, holding their ankles or something. That actually happens every few years, usually making the crowd very angry because they don’t understand why the refs do not call offside then.