This is where things get a bit risky. I’ve chosen to use entity here to avoid the controversy around content type. But of course entity has a technical meaning in Drupal—one that is broader than the Drupal meaning of content type. For example, an image plus its associated metadata is a Drupal entity, but it’s not a content type. Here I’ll use entity to refer to logically connected independent sets of attributes and nested entity to refer to logically connected sets of attributes that are not meant to be consumed as independent things.