In Yii, modules are self-contained packages that operate independently of a Yii application but must reside within an existing application or module. Modules can additionally have as much or as little integration with our core application as we desire. In many aspects, modules are identical to Yii applications in that they have controllers, models, views, configurations, and components. This functionality allows us to deploy and manage code independently of our main application. It also provides us with greater usability if we choose to reuse our module across multiple projects. For our application, we'll be using our modules solely to separate the management of our application from the presentation layer and to independently deploy our application without having to make changes to our main application code.