What are .tpl files? PHP, web design

Templates. I think that is Smarty syntax.

That looks like Smarty to me. Smarty is a template parser written in PHP.

You can read up on how to use Smarty in the documentation.

If you can't get access to the CMS's source: To view the templates in your browser, just look at what variables Smarty is using and create a PHP file that populates the used variables with dummy data.

If I remember correctly, once Smarty is set up, you can use:

$smarty->assign('nameofvar', 'some data');

to set the variables.