What makes modules so easy to use is the convention-over-configuration approach that lets you use expected file and folder names instead of manually configuring things. Here are some of the high-level conventions that modules use.
/modules/ModuleName/ModuleConfig.cfc
The settings for a module is stored in the ModuleConfig.cfc file in the root of the module. This CFC is automatically created and its settings extracted when the module is loaded. It has lifecycle methods like onLoad() and onUnLoad() that will be called automatically if they exist. This CFC will also be loaded up as an interceptor, so any method names that match interception points will be registered. Read more about module configuration here.
/modules/ModuleName/models/
CommandBox ships with WireBox, which is the glue that holds everything together. Your custom modules can contain as many models as they like. Place your CFCs (beans, services, etc) in the models folder and WireBox will automatically map them as modelName@moduleName so they can easily be injected into any other model, interceptor, or command CFC.
/modules/ModuleName/commands/
One of the primary purposes of modules is to serve as a delivery mechanism for custom commands. All command CFCs should be placed in the commands folder inside your module. Any CFCs there will automatically be registered when the module is loaded, and will be available in the help command, as well as tab-completion, etc. To create namespace commands, create extra sub folders inside the commands folder that match the name of the namespace. Read more about command configuration here
/modules/ModuleName/interceptors/
Any interceptor CFCs packaged inside a module should go in an interceptors folder. Interceptors are not loaded automatically though. You'll need to reference the component path in your ModuleConfig.cfc. The path that points to the interceptors folder can be resolved in your config file as #moduleMapping#.interceptors.MyInterceptorName. Read more about interceptor configuration here
/modules/ModuleName/modules/
Wait, what-- modules can have their own modules?? Yep, we call that "module inception" and it's one of the most powerful features of modular development. If your module depends on another CommandBox module, then specify that dependency in your module's box.json and it will automatically be installed for you inside your modules folder.