There are two types of persistence models in Magento: simple and Entity–attribute–value (EAV). The term entity is tossed around interchangeably between the two types of models. We can think of an entity as any persistable model.
The Subscriber entity of the Magento_Newsletter module is an example of a simple model. We can see that it's comprised of the following:
- A model of type Magento\Newsletter\Model\Subscriber extends Magento\Framework\Model\AbstractModel
- A resource model of type Magento\Newsletter\Model\ResourceModel\Subscriber extends Magento\Framework\Model\ResourceModel\Db\AbstractDb
- A collection of type Magento\Newsletter\Model\ResourceModel\Subscriber\Collection extends Magento\Framework\Model\ResourceModel\Db\Collection\AbstractCollection
The Customer entity of the Magento_Customer module is an example of an EAV model...