Entities, nodes, and fields
When working with Drupal, one of the most important concepts to understand is that you are not just building pages, you are building page containers that consist of components. These components are made up of things called entities.
Everything you create in Drupal is referred to as an entity.
Most viewable content you create will be of a particular type of entity known as a node entity.
You may often hear the terms "node entity", "node type", and "content type" interchanged routinely, so it's a good idea to think of these terms as synonymous.
There can be many different types of node entities in any given site, but in the standard installation, there are only two content types (node types) defined ...