You can think of an Angular/AngularJS module as a container for the different parts of your app – controllers, services, filters, directives, etc.
Most applications have a main method that instantiates and wires together the different parts of the application.
Angular apps don't have a main method. Instead modules declaratively specify how an application should be bootstrapped. There are several advantages to this approach:
- The declarative process is easier to understand.
- You can package code as reusable modules.
- The modules can be loaded in any order (or even in parallel) because modules delay execution.
- Unit tests only have load relevant modules, which keeps them fast.
- End-to-end tests can use modules to override configuration.
