So there you are, offside-lite (ie offside, but not yet having committed an offside offence), watching as the ball arches towards the opposition goal mouth. Your new best friend, the opposition goalie, is out of position, but fortunately he manages, with an athletic dive which sends a thrill up your spine, to throw himself towards the ball. It passes within inches of his outstretched fingers, ricochets off the cross-bar at an angle and heads back into play.

As all this happens, the erstwhile second-to-last-opponent, the goalkeeper’s previous bezzie mate, is rushing forwards to defend the goal. He passes you going in the other direction as you try to get out of the way. Both he and the ball are now in front of you, so you are not offside, although, remember, you were offside at the moment your tream-mate kicked the ball. You are therefore faux-offside, aka offside-onside, and should still not interfere with play. 

And indeed this fits entirely with your own thinking, but as you attempt to fade back into the melee of players around the goal-mouth you catch sight, out of the corner of your eye, of the ball arcing towards you, causing you to twist away in an attempt to avoid it. But, disaster! The ball catches your shoulder, rebounds off and bounces over the opposition goal-line before the helpless eyes of the goalie, who is still trying to get up after his incredible diving almost-save. Your own side and your fans all cheer, the other side’s fans yell indignantly, and your opponents all yell “Offside! Oy, ref! Offside!”

And they are correct, for you have, at this point, committed an offside penalty (“offside penalty”) and you hear the referee blow his whistle to stop the game.

Now, is everybody clear what happened there? Oh, for heaven’s sake. How much simpler can I make it? Don’t you want to understand the offside rule before the final? Oh. Right then. Well, just read your book quietly until the bell goes. The rest of you, we’ll be tackling this again in More Tomorrow.
That was The Footballing Fact Of The Day, part 9. I thank you