In a typical multi-layered application, the Model usually refers to the database entity (a class that is directly mapped to a table in the database). On the other hand, a DTO (Data Transfer Object) is used to transfer data between layers of the application, particularly when you want to decouple internal models from external representations.

However, some companies may not strictly follow this naming convention. For example, they might suffix their database entities with "DTO" or refer to DTOs as "models." While this isn't necessarily a bad practice, it can lead to confusion, especially for junior developers who are trying to understand the architecture.

Typical Flow in a Multi-Layered Application:

1. View (Frontend):
   Sends user input and requests to the backend.

2. Controller:
   Receives data from the frontend and forwards it to the service layer. It may also handle some light aggregation or orchestration logic.

3. Service Layer:
   Fetches entities from the DAO, performs business logic, and maps entities to DTOs (if needed).

4. DAO (Data Access Object):
   Handles CRUD operations and returns entities from the database.

5. Backflow:

   • DAO returns entities to the Service layer.

   • Service processes data, applies business logic, and returns a DTO to the Controller.

   • Controller sends the processed data back to the View (frontend).

In some projects, DTO mapping may also occur at the controller level. This depends on the architectural design and project requirements. However, directly exposing database entities to the frontend is generally discouraged. Instead, entities should be converted to DTOs that only include the required fields. This ensures encapsulation, enhances security, and prevents unnecessary data exposure from the database schema.