Bundles are most utilized in the configured field levels via the Field and Field UI modules. When you create a new field, it has a base storage item for its global settings. Once a field is added to a bundle, there is a new field configuration that is created and assigned to the bundle. Fields can then have their own settings for a specific bundle along with form and view display configurations.

Content entity bundles work just like any other configuration entity implementation, but they extend the usability of the Field API for your content entity types.