Entity, fields, bundles, and display modes
All contents managed by Drupal are stored in some entity type.
In Drupal, an entity is a data structure representing a specific content or information type. Entities define the structure and behavior of different kinds of content on a Drupal site, such as nodes, users, taxonomy terms, comments, media.
Note
Drupal uses the term content on the web UI and documentation to refer to a specific entity type, which in code is called a node. Even if you look at the canonical URL for a content page (one of the pages that you can reach from the Content menu on the toolbar), you see that it’s in the form node/1, where 1 is the ID of the node that Drupal will render in the main content area of the page.
Each entity type has its properties that define the information it manages. For example, a node entity type might have properties such as a title, body text, and author, while a user entity type might have properties such as a username...