What is server and client side?

Question

client-server

Good day! Recently I came across the fact that no matter what devices you want to program for (let's say mobile development), you must know some server language to create the server and client parts.
1) Please explain what the server and client parts are
2) How to create these parts and how to work with them?
3) Whether it is obligatory to create the server. and client. parts?

Answer 1

Any system on the web consists of 2 parts.
Part 1 (client part) is actually the program that you use on your computer. For example browser.
The browser itself does nothing. He can only display information received from somewhere.
Accordingly, the 2nd part of the system is introduced - the server part.
It somehow interacts with the client (browser, phone, etc.) in such a way that the user of the client can get some useful information.
That. the client sends a request to the server. The server processes it and returns a response. The client displays this response.
For the client side, you need (as a first approximation): HTML \ CSS, JavaScript or create a program (for android, for a computer, etc.)
For the server side, you need (to a first approximation): PHP, a web server (apache, nginx), a database (MySQL, Postgresql, MongoDB, etc.) or another program that can interact with the client in some way.
You can not create a client-server architecture. You can make a regular program and work with it.

Answer 2

The last two tags are off topic.