Manual:MediaWiki.php

Description
Among other things this file contains:

Function performAction which performs most actions, including creating the HTML. For example, in the case of viewing a page, function "view" in Article.php is called.

Function (called by index.php) which by  flushes out all HTML.

Hooks

 * Manual:Hooks/ArticleFromTitle
 * Manual:Hooks/UnknownAction