Any introduction to anything should start with a clear statement of what it is and why you might want to use it. I find this a particular problem with computer language topics; I don't know yet why The Author find This Thing so useful so tell me up front a few benefits I might get from investing my time in learning it. Unfortunately, the people who are best at using something are not always the best at communicating it.

This is particularly important for audiences like teenagers, who already have multiple private and public actors competing for their attention and future economic potential.