The Yii documentation states: > An application module may be considered as a self-contained sub-application that has its own controllers, models and views and can be reused in a different project as a whole. Controllers inside a module must be accessed with routes that are prefixed with the module ID. So, in practicallye, a module can be handled just aslike an application, but with only minor differences. Supposinge you were havinghad a custom component 'foo' in your application:

```php```

A...and you need to move it inside a module called 'bar':

```php```

Now instead of using the component as usual: ```php Yii::app()->foo ``` You need to call it like thiscall it from within the module: ```php Yii::app()->controller->module->foo ``` As you can see, your module is indeed just another application, and you can configure any parameters as you'd do with your "root" application. The only organizatoryional differences are: + a module has a module "entry point", the FooModule which extends CWebModule, w. Whereas the root application is bootstrapped by the framework itself, starting with your entry script (index.php) + the application's SiteController is called inside a module DefaultController