> For the complete documentation index, see [llms.txt](https://docs.digitalriver.com/woocommerce/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.digitalriver.com/woocommerce/1.0-1/developer-documentation/module.md).

# Modules

### Core modules

A module is a piece of program in a plugin that performs a particular task, or it can function with other modules. The WooCommerce plugin has seven core modules: 

* [`Logger`](/woocommerce/1.0-1/developer-documentation/module/api-logger-module.md) module
* [`OrderManagement` ](/woocommerce/1.0-1/developer-documentation/module/ordermanagement-module.md)module
* [`ProductCheckout`](/woocommerce/1.0-1/developer-documentation/module/productcheckout-module.md) module
* [`ProductMetaFields`](/woocommerce/1.0-1/developer-documentation/module/productmetafields-module.md) module
* [`ProductSync`](/woocommerce/1.0-1/developer-documentation/module/productsync-module.md) module
* [`Settings`](/woocommerce/1.0-1/developer-documentation/module/settings-module.md) module
* [`TaxCalculation`](/woocommerce/1.0-1/developer-documentation/module/taxcalculation-module.md) module

A module is a piece of program in a plugin that performs a particular task, or it can function with other modules.

### Module interface

The module interface is for any module that needs to be registered with the plugin. Custom modules need to implement this interface for registration.

{% tabs %}
{% tab title="PHP" %}

```php
interface Module {
    /**
     * Initialization of module.
     *
     * @return void
     */
    public function init(): void;

    /**
     * Return module name.
     *
     * @return string
     */
    public function name(): string;
}
```

{% endtab %}
{% endtabs %}

### **Method description**

* **$module->name()**: This method needs to return module name. 

  The module name can be alphanumeric without spaces. Dashes and underscores are allowed.
* **$module->init()**: Any actual work or initialization activity related to the module should go inside this method. 

  **Example**: You can add any hooks or call necessary functions/methods inside `init` to run the module.  

{% hint style="info" %}
Do not explicitly call the `init` method. The plugin calls the`init` method during module activation (under the hood). 
{% endhint %}

### **Register the custom module**

To register the custom module:

1. Create the main module class that either implements the `Module` interface or extends the `BaseModule` abstract class. Since most of the modules will only be functioning when you enable the Digital River payment gateway, it makes sense to extend the `BaseModule` class.   
2. Add the module name by returning the `name` method to the `Plugin::$active_modules` list.