What are the main processes that can be in the back-end of a mobile application?

Question

Software design

The question will seem silly, but I'm just - just (the first day) starting my journey in learning development (before that I was only engaged in prototyping and design). And I had difficulty with the selection of processes in the work of the application-backend bundle.
If we take the work of a mobile application that sends file data to the application server and receives data from the database from there, what general processes can be distinguished here?
In my understanding, this is data transport to the API, user authentication, data validation, data conversion (if necessary), transport and sending (receiving) data to the application.
So, (if you do not use ready-made solutions), logically, I will need to
1. Create an application
2. Deploy a database with data tables where data from the upload file and user data will
go 3. Teach the application to access the server
4. Describe data validation criteria
5. Write user authentication
6. And here's something else that will return data to application
Fly with cutlets, probably, but I did not find materials with an accessible explanation in the public domain at all. Please help me understand where to look and how to separate flies from cutlets, or drop links where you can see it.

Answer 1

From the position of developers, in general terms, a mobile application sends some kind of request to the server, and when it is received, it processes and returns a response, then the response is processed. A mobile device is controlled by a user, has its own user interface, has some data on the device itself and is able to exchange them with a server located somewhere remotely and accessible via the Internet.
The server has an API that exposes a set of public services to the mobile app and possibly other views.
User authentication may be present on the server if personal services need to be provided. After identifying the user, the program on the server performs some actions. Perhaps it updates the data in the DBMS and issues a response.
The developer of a mobile application should be able to build a user interface in which the business logic of the application and the logic of interaction with the server will be thought out.
The developer of the program on the server must be able to build a program that will receive various requests from clients and be able to process them according to business logic, as well as think over the data structure in the DBMS and how to interact with it.
It is customary to perform data validation on both the client and the server.
In building a mobile application and a server application, there are a lot of nuances in addition to the technologies used.
From the position of a product manager, there are also many concerns.