Remove query strings from static resources in template.php
The only reason you'd want do this is to remove any cache busting query parameter. These are query parameters that are appended to a URL (e.g. www.example.com/js/some_file.js?b= 1433781670 &amp; www.example.com/css/some_file.css?b= 1433781671 ) to prevent browser caching. 



As the tutorial probably explained, you'd only want to do this for static resources (i.e. any web resource like a CSS/JS/Image file that will never change) so that the browser will cache the static resource. 

As for the template question you can place the MYTHEME_processs_html() function anywhere in template.php (if you don't have one, create it). On top of that, the only thing you'd need is to replace MYTHEME with the short name of your theme and flush your theme cache.

If you're new to Drupal I'd recommend avoiding this for now; unless you're sure there's only static CSS stylesheets that can safely have its cache-busting query string removed, you can end up with a scenario where modules/themes aren't displaying correctly because the cache busting query parameter was needed.