The angular.module is a global place for creating, registering and retrieving Angular modules. All modules (angular core or 3rd party) that should be available to an application must be registered using this mechanism.

Passing one argument retrieves an existing angular.Module, whereas passing more than one argument creates a new angular.Module

Module

A module is a collection of services, directives, controllers, filters, and configuration information. angular.module is used to configure the $injector.

// Create a new module
var myModule = angular.module('myModule', []);

// register a new service
myModule.value('appName', 'MyCoolApp');

// configure existing services inside initialization blocks.
myModule.config(['$locationProvider', function($locationProvider) {
  // Configure existing providers
  $locationProvider.hashPrefix('!');
}]);

Then you can create an injector and load your modules like this:

var injector = angular.injector(['ng', 'myModule'])

However it's more likely that you'll just use ngApp or angular.bootstrap to simplify this process for you.