As mentioned in other answers, there are no files or flow of pages. index.php
takes the values of $_GET['q']
and calls the appropriate functions to dynamically generate pages.
You can use $_GET['q']
to access those "file path" portions of the URL, but the more Drupal way is to use arg()
, for example, with a path of http://localhost/node/5
, you could access node
with a call to arg(0)
and the 5
with a call to arg(1)
. This is the Drupaly way to access those parts of the URL.
Drupal also provides utility functions for getting at the base path. The L function l()
formats links and takes care of base path for you as well (you just write relative links, it appends base path as necessary); base_path()
will return the global of the same name; drupal_get_path()
takes some extra Drupal-specific arguments and will generate paths to things like modules and themes with the base path taken care of as well.
Were you looking for more information? Refine your question based on these answers, and check out Drupal's API documentation: http://api.drupal.org/