There are lots of feature in angularJS and some of these are as follows: -
Directives in angularJS extends HTML code to provide new behaviour.
Ng represents angular.
ng-app directive is the beginning directive of angularJS. It is used to auto bootstrap angularJS application. We generally use this directive at root level like inside html tag or in body tag.
We use data-ng-app directives to validate HTML5 because it will consider data-ng-app as custom attribute. If we will write only ng-app then html5 validator throw an exception.
Module in angularjs is just like container which is having the business logics, controllers, services etc. it is just like main. As main contain the startup logic and in angularjs we use module for startup.
$scope is the kind of object which represents the application model. It is used to pass data between view and controller. We can add properties in this scope and we can use it.