Why we need DTO and Data be part of a design pattern in MVC?

I'm new to MVC and .NET.. Being a beginner, I'm now able to develop in simple MVC with the entity approaches available.I understand that splitting our code into various layers saves/improves a lot of "whatever you put in this quotes". I wanna get a clear picture of why and where we should use the layers such as Data,DTO,Services,API,etc,.

It would be of great help if I find the solution here to begin my career in .NET. Thanks in advance