Simple flying jumping sidekick, like your opponet is just going to stand there while you come running at him and jump with that foot going right at him, please the movies are great but this kick is worthless and yet it get tought by everyone except me but my students learn it from vido games and movies.
If they move to your outside you can follow them with your kick, they move, they think they have avoided the kick and you still get them. I have seen it and done it many times. The best way to do one is to run normally and then, without warning, suddenly jump and kick, that way they just think you are running at them and not going to kick. A lot of students, when learning the kick will often make some unusual steps just before jumping which gives it away until they know better. Some possible uses could be if you have to clear an object on the ground to kick someone attacking someone you are trying to protect while their not looking. Also if you are getting chased by someone and his friend jumps out in front of you to block your path you can kick them with it and continue on your way, barely missing a step. That's why they are taught to everyone.