Drupal’s terminology can be confusing when you are not already familiar with it. I have gathered in this post essential terms that will should make non-technical people (or simply people new to Drupal)'s life easier. I'm happy to add to this list if people identify additional useful terms they feel need further definition.

Core

Core refers to the code files that make up the default functionality of a Drupal site when you download it from drupal.org.  The functionality includes menu management, user management, system administration, design and layout, etc. Additional functionality can be included by adding modules to the Core code.  

Modules

A module is a packaged set of files that adds or modifies existing functionality when installed.  Modules are called plug-ins, extensions, or add-ons in other software projects. A good analogy is to think of Core as your Smartphone when you have just bought it. When installing applications, you are increasing the functionality of your smartphone the same way modules add functionality to Drupal Core.

Node

A node is a piece of content such as a blog post, a article, or a poll. This piece of content is made up of fields (title, body text, creation date, etc.). Drupal has several ready-made types of nodes (aka "content types"), each with fields appropriate for its intended use; you can modify these to your liking or create completely new content types.

"Node" is not the same as a "page", i.e., a web page. Drupal creates pages out of many components: typically one or more nodes, surrounded by a header, some menus, possibly sidebars with blocks of extra information, and so on. To clarify the difference: users create nodes (articles or other content); Drupal creates pages out of those nodes and other page elements.

Content Types

A single web site could contain many types of content, such as informational pages, news items, polls, blog posts, real estate listings, etc. In Drupal, each piece of content is called a node, and each node belongs to a single content type, which defines various default settings for nodes of that type, such as whether the node is published automatically and whether comments are permitted. When you first install Drupal Core, you will have two content types defined: "Article" (blog post) and "Basic page". When you enable other core and contributed modules, you will find that you have other content types available; you can also create your own content types.

Content

The text, images, and other information on a web site. Besides nodes there is more content on a typical Drupal site, such as comments and file attachments.

Taxonomy

Taxonomy is Drupal’s system of categorization.  The word "taxonomy" refers to the system for tagging and organizing content by keywords. Drupal calls those keywords "terms" or “tags”, and groups of terms "vocabularies". A site can have an unlimited number of vocabularies, that can each contain an unlimited number of terms. Sometimes you will want to create a "controlled vocabulary," where content authors can assign terms that have been predetermined. If so, you will need to add those terms to your vocabulary in advance.

An alternative model for organizing information is the use of "tags." User-defined tags can be added to Drupal content on the fly.

Block

A block is simply a content area that can be modified to display content in a specific way. Blocks can be used to display items like related events, promoted content or calls to action in the same format on multiple pages without having to recreate it again and again.

Basic Page

One of two content types that are enabled in the standard installation profile. Typically basic pages are used for static content that can (but are not required to) be linked into the main navigation bar.

Entity

Any defined chunk of data in Drupal. This includes nodes, comments, taxonomy terms, files, etc. Contributed modules can define custom entities. Each entity type can have multiple bundles.

Field

Elements of data that can be attached to a node or other Drupal entities. Fields commonly contain text, image, or terms.

Roles

Roles are a grouping of permissions for accessing, creating, editing, and deleting content and managing different aspects of the site.  A role is then assigned to a user and that user has the permissions assigned to the role.  For example, if a role name ‘editor’ is given the ability to create and edit articles and the editor role is assigned to Ellen, the links to create and edit articles are displayed to Ellen when she is logged in. If Ellen sends Joe a link to edit an article and Joe doesn’t have the editor role assigned to his account, he will be shown an “access denied” message.

Users can belong to more than one role. Two roles, authenticated users (those users that sign up for an account) and anonymous users (those either without an account or not logged in), are supplied by default with Drupal installations. Drupal allows creating additional roles.

Theme

The theme is a collection of files and images that determine the look and feel of a site (layout, color scheme, etc.). A theme contains elements such as the header, icons, block layout, etc.

Views

A contributed module which allows site developers to build a simple graphical interface for creating lists of various Drupal objects; most notably users and nodes. Views permits selection of specific fields to display, filtration against various node attributes, choice of basic layout options (i.e. list, full nodes, teasers, etc.), and other more advanced features. Many Drupal sites use Views extensively. For example, a view could show a list of users that have registered in the past month, or a list of line items on an order form, or a list of unpublished content. 

WYSIWYG

What You See Is What You Get. An acronym used in computing to describe a method in which content is edited and formatted by interacting with an interface that closely resembles the final product.

Additional resources

• Drupal Concepts: https://www.drupal.org/documentation/concepts
• Drupal Glossary: https://www.drupal.org/glossary
• Drupal HowTos: https://www.drupal.org/documentation/customization/howto
• Drupal.org: https://www.drupal.org/
• Drupal Content Tutorials : https://www.siteground.com/tutorials/drupal/articles-pages.htm
• Understanding Drupal: https://drupalize.me/videos/understanding-drupal

Resources in French:

• http://drupalfrance.com/recettes
• http://www.drupalfacile.org/