Composer is the preferred dependency management solution for PHP, is used by Drupal core, and is becoming increasingly popular for managing the modules and themes used for a Drupal project.

Use the Configuration API to access configuration data stored by a module, provide default configuration, create settings forms, and other tasks such as overriding settings for a local environment.

Controllers are the portion of a Drupal module that handle responding to an incoming request with the appropriate response data.

Cascading Style Sheets (CSS) files are added as an asset library through a theme’s libraries configuration file. HTML attributes, including classes and IDs, are commonly added in template files with Twig.

The Git version control system can help you keep track of changes in your codebase and make sure you don't unintentionally lose work.

Drupal's Routing API maps the URL of an incoming request to the code responsible for generating the content that is rendered in response.

Keeping a Drupal site secure requires monitoring security announcements, performing regular updates, and knowing how to properly use Drupal’s APIs to write secure code.

The Drupal Composer Project provides a scaffold for starting a new Drupal project and managing that project's dependencies with Composer. It was created before the drupal/recommended-project Composer project template was developed, which is the current best practice method for creating a new Drupal site with Composer.

HTML and CSS are the foundational languages for how browsers display web pages.

YAML, which stands for YAML Ain't Markup Language, is a human-readable data serialization format that's been widely adopted in a variety of use cases in Drupal.

Performance and scalability determine how fast your application can serve a page and to how many users at a time.

Events are one of the ways that module developers can alter or extend Drupal without modifying existing code.

Debugging your Drupal codebase can be made substantially easier by learning how to enable and configure the Xdebug PHP extension.

Caching in Drupal is controlled by Drupal's Cache API which is used to store any type of data on a permanent or temporary basis. Some types of data tend to take a long time to compute, but utilizing the Cache API in your module can help your site load data more quickly.

Learn about resources to guide you through the process of updating a module or theme to the latest version of Drupal.

In Drupal’s core library there are a number of utility functions and classes that, as a module developer, you will find make your task easier or less tedious.

Plugins are one of the ways that module developers can write code that extends Drupal. The Drupal Plugin API allows a module to provide functionality in an extensible, object-oriented way.

Upgrading is the process of moving your site from a previous major version of Drupal to a newer version, for example from Drupal 7 to Drupal 8 or Drupal 9 to Drupal 10.

The Migrate API can be used to import content from an older Drupal site (Drupal 7 or older), or any other data source, into the current version of Drupal.

Themes provide the HTML, CSS, JavaScript, and other assets that are responsible for the look and feel of your site.