AngularJS is a JavaScript MVC framework developed by Google that lets you build well structured, easily testable, declarative and maintainable front-end applications which provides solutions to standard infrastructure concerns.
A module is a container for different parts of your application. Or You may think modules as a main() function in C programming, which bind together different parts of the application as same as Modules specific how Angular application should Bootstrap.
AngularJS allow us to embed HTML page within another HTML page using ng-include directive.
If you are from the jQuery background for hiding and showing element you generally use show() and hide() function or may be used css() function when an event occurs. AngularJS provide directives for it also i.e, ng-hide and ng-show.