Alright, so hopefully that video helped. However, the most complicated thing about off sides is not only the definition or the fact that it relies on the last defender or the ball. The most frustration thing about off sides is the refs.
Since the side line refs have to call it, they need to be paying attention to everything at once. They have to see where the player is in relation to the last defender and also at what time the ball is passed to the player who might be off sides. One of the main things about the off sides rule is that if the ball is kicked before the player moves into the off sides position, then they are not off sides.
About 50 percent of the time, the refs get the off sides call wrong. This rough percentage increases when the defending team constantly pulls the off sides trap. This happens when the defense pulls forward fast and quick right before the ball is kicked. This causes the forward to be off sides before they even realize that the defenders moved.
Here’s a clip of the Netherlands playing a great off sides trap against Australia. If you notice on the second play by play, the defense is almost all moved away from the forwards before the ball is kicked.
This takes a lot of concentration and communication. Also, the refs have to pay close attention to this. The only thing that really stinks about the off sides trap is that if the ref misses it, then they have an open net to score. This is why most teams try to avoid the trap and just rely on their defense to clear the ball away from the net. The off sides trap must be carefully practiced and executed in order to get it right.
If there are more questions about off sides then comment below.