xdebug - what is a PHP extension?

Question

I am learning to use xDebug. Before I dive deeper, I'd like to clarify some concepts that have been bothering me for a while.

Firstly, my way of using PHP is through VPS or local environment like xampp. Before I can actually use xDebug, I need to understand what it is. And it is a "PHP extension". What exactly does "PHP extension" refer to here? Is it a library comprised of functions? Or is it some lower level program that need to be installed along with PHP?

From these questions you can see I am a beginner, unfortunately, the xDebug website is not very friendly to us beginners, I have read a lot but understood little. And I think what an "extension" is is the meta question I need to get answer before I can understand other documentations.

Answer 1

An extension is a library of new classes, methods, an interfaces that extend the php language, an extensions works like a toolbox, some are include in the core PHP but others you have to install individualy. in this case XDebug let you to debug your php code, include monitoring, and profiling tools.