How to properly implement the API for Joomla 3.x?

Question

Joomla

Hello colleagues.
In this system, sorry, zero! Components, plugins, modules - for me it's like one and the same thing...
I would like it not to be chewed, but at least given an understanding in which key to move.
My task is super simple - to file an elementary API in Joomla, and in its admin panel itself, the ability to enter a certain key (an elementary form with one field) to authenticate when requesting this API.

Answer 1

In any case, you will have to learn at least what a plugin is...
In the minimum case, a plugin that will use the built-in Joomla component for AJAX communication will suffice