Modules are bundles of primarily PHP code that extend Drupal in order to add new features or alter existing functionality.

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.

Patches are used to describe modifications made to one or more code files, and can be used to share those changes.

Drupal includes the PHPUnit testing framework. This enables us to write unit and functional tests to attempt to minimize the number of bugs in our application.

In order to run a Drupal site, the web server you are using must meet minimum technical requirements.

Drupal's vendor-agnostic database abstraction layer provides an API that can query different underlying databases.

Tools and workflows for deploying code and configuration changes from one environment to another with Drupal-specific considerations.

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.

The process for keeping Drupal core and contributed modules and themes up to date with the latest security and minor version releases.

Learn about Drupal’s configuration system and how to manage configuration with both the administrative user interface and command-line tools.

Comments are a content entity type that allows users to leave commentary associated with a specific piece of content.

PHP: Hypertext Preprocessor (PHP) is a popular interpreted programming language that is especially suited for web development. Drupal core and all contributed modules are written in PHP.

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.

Drupal has an amazing community of people who create the software and help each other make the best use of it. This is one of the main benefits of using Drupal — and everyone should take advantage of that.

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.

A layout can describe how various components are arranged on various levels—from an entire page from the header to the footer, to just the “middle” where the dynamic content goes, to individual components. It can apply to templates for managed content or one-off designs for landing pages.

Development environments provide a sandbox where you can work on your application without affecting the live site.

A reliable backup will allow you to restore your site if something goes wrong.

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.

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