Angular.js - directive is called but used nowhere

Following code is working although I didn't find authDemoApplication somewhere outside this file, not in *.js, nor in .html files.

angular.module('angular-auth-demo', ['http-auth-interceptor','content-mocks'])
  .directive('authDemoApplication', function() {
  });

So, how is this directive working and where to read about this method of calling?