What is Data Transfer Object?

Question

What is a Data Transfer Object?

In MVC are the model classes DTO, and if not what are the differences and do we need both?

Answer 1

1. To me the best answer to the question what is a DTO is that DTO's are simple objects that should not contain any business logic or methods implementation that would require testing.
2. Normally your model (using the MVC pattern) are intelligent models, and they can contain a lot of/some methods that do some different operations for that model specifically (not business logic, this should be at the controllers). However, when you transfer data (eg. calling a REST (GET/POST/whatever) endpoint from somewhere, or consuming a webservice using SOA, etc...) you do not want to transmit the big sized object with code that is not necessary for the endpoint, will consume data, and slow down the transfer.