13. Directives
A directive is a behavior or DOM transformation
which is triggered by the presence of a custom attribute,
element name, or a class name.
A directive allows you to extend the HTML vocabulary in a
declarative fashion.
AngularJS's developer guide
(http://docs.angularjs.org/guide)
16. Controllers
A controller is a JavaScript constructor function that
is used to augment the Angular Scope.
AngularJS's developer guide
(http://docs.angularjs.org/guide)