Although you have written no code, many objects have been created to make this work. Figure 13.19 is a diagram of some of them.
Figure 13.19 Objects in CarLot created by Core Data
The NSPersistentDocument reads in the model you created and uses it to create an instance of NSManagedObjectModel. In this case, the managed object model has one NSEntityDescription (which describes the Car entity). That entity description has several instances of NSAttributeDescription.
Once it has the model, the persistent document creates an instance of NSPersistentStoreCoordinator and an instance of NSManagedObjectContext ...