A feature of Drupal that makes it desirable is the ability to customize it through modules. Whether custom or contributed, modules extend the functionalities and capabilities of Drupal. Modules can be used to not only extend Drupal, but also to create a way to provide configuration and reusable features.

This chapter will discuss how to create a module and allow Drupal to discover it, allowing it to be installed from the extend page. Permissions, custom pages, and default configurations all come from modules. We will explore how to provide these through a custom module.

In addition to creating a module, we will discuss the Features module that provides a set of tools for exporting the configuration and generating a module.