Where are the Joomla CMS core files?

Question

Joomla

I don’t find any normal documentation for Joomla ...
Tell me, please, where are the files of its core - what is responsible for the output of the socket final buffer reset and die() ?

Answer 1

No documentation??? Are you okay at all? And this is what: https://docs.joomla.org/Main_Page
If you can’t google elementary things, then you won’t understand the core even more.