Hey Gary,
There are a couple of aspects to this, and definitely an interesting question.
First - you can - very simplistically, for the sake of the argument here - look at an application as having two main responsibilities - the front end and the back end. The REST API would be the back end. And to use your terminology - the REST API IS the application. The course also touches on (but doesn't go to far into)
Angular JS - so the front-end responsibility as well.
Now - if you have in mind more traditional MVC style of applications - this course is not about that. That's a different way to build an app - and it's definitely not a goal of this course to cover the older, MVC-style of architecting a system.
Hope that answers your question. Cheers,
Eugen.