Files name listed on the Theme Editor

Hello,

On the theme Editor, the files listed on the Theme Files are most of the time without extension (ie: Single Post for single.php).

I added some files via ftp but these files appear on the theme editor with the extension. May some one explain me how to have a name without extension so i may call it (<?php get_sidebar2(); ?> and not <?php get_sidebar2.php(); ?>

thanks