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

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.

For the Drupal developer, Docker is a way to provide a local development environment to run web server software.

The Render API consists of a standard format for describing data using structured arrays and a process for converting those arrays into the HTML a user sees when interacting with a Drupal site.

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.

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.

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

Services are objects that encapsulate the code for performing specific tasks in a reusable and decoupled way.

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.