How wp maps urls into files

Go to “Pages” and find the page with the ID. Open it in editor. On the right hand side, look for “page attributes”. You can add php files here. All you have to do is, create a PHP page under your theme, and add this to your beginning of the file:

<?php
/*
 Template Name: A PAGE NAME HERE
 */

Reload, and your file shows up with the A PAGE NAME HERE within the select box.