In Drupal, routes help map the URL of an incoming request to the code responsible for generating the content that is rendered in response.

A site's main navigation elements, whether they be in the header, footer, or sidebar, are composed of links built using Drupal's menu system. Drupal allows site administrators to build menus while also allowing module developers to add and alter menus in code.

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

Drupal provides a standard, secured method for module developers to add forms to a Drupal website. Learn how to use the Form API to build, validate, and submit a custom form.

Entities are the fundamental building blocks that make up any Drupal site. Having a good understanding of the Entity system is an important part of ensuring the data model of your Drupal site is set up properly.

Fields are the building blocks of Drupal's powerful content modeling system. The Field API allows for the development of custom field types to suit almost any data display and collection needs.

Hooks allow modules to alter and extend the behavior of Drupal core, or another module. As a Drupal developer, understanding how to implement and invoke hooks is essential.

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.

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

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.

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.

Debugging is the practice of troubleshooting an application through the use of tools and processes in order to find and fix bugs, or better understand the underlying code.

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.

JavaScript files are included by a module or a theme by creating an asset library. Using this asset library system you can selectively choose which files to load, overwrite existing files, or customize them to suit your needs.

Twig is a template engine for PHP, which is the language used in Drupal. Twig can be used to design templates in generic PHP applications as well as Drupal themes.

Debugging is the practice of troubleshooting an application through the use of tools and processes in order to find and fix bugs, or better understand the underlying code.

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

The Cache API is used in Drupal 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.

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.

As an open source project, Drupal depends on community contributions in many forms including documentation, code, translation, speaking, organizing events, mentoring others, and even donating money.

Coding standards provide a set of rules for how your code should be formatted, and best practice guidelines for naming conventions and the location of files.

Drush is a command line interface that enables you to interact with your Drupal site without clicking around the graphical user interface (GUI).