PHP is parsed (or executed) at run time by the webserver. PHP can parse HTML but HTML can't parse PHP. If it's an HTML template it's possible it was created in a PHP script.
HTML templates often use things like BBcode to parse the input (eg POST or file) and changed it eg ; ) to a wink emoticon image or something. PHP parsed the input, chaged the wink text into HTML calling on the image.
I hope that helps to clear it up and I've not confused the hell out of you