This is a technique used to defend from someone when you are underneath them and they are choking you. It is imperative that you know how to escape from this as a lot of people have been killed this way. Practice the technique as much as possible before you start trying to do it live or fast paced.
One of the most crucial aspects of self defense and staying safe is mental awareness or what the Japanese refer to as "zan-shin", which loosely translate to awareness of danger. You will always fare better in a confrontation if you get to see it coming and are cognizant when you are in situations or places that place you or your loved ones in danger. The following video will give you some pointers on awareness.
When we talk about soft targets in self defense we are talking about targets on any individual that are equally easy to attack whether that person is big and strong or small or weak. It doesn't matter how much a person can bench press, their knee will still break with the same amount of force. The following video will explore these concepts a little more.
The Book of Five Rings is a text on kenjutsu and the martial arts in general, written by the swordsman Miyamoto Musashi circa 1645. However it is much more than that, the strategies Musashi advocates in this book can be applied to any form of competition. There have been various translations made over the years, and it enjoys an audience considerably broader than only that of martial artists: for instance, some business leaders find its discussion of conflict and taking the advantage to be relevant to their fields. Here is an online version of it if you'd like to investigate Musashi's teachings further.
If you're having a hard time getting your sluggish kid away from video games and getting them into something real and good for them, you should probably try making exercise time a bit more adventurous by mixing in some basic martial arts moves. Let them try these five simple karate exercises, and you'll be heading them in the right direction in no time.