.. I don't know how you wouldn't know which file to use.

you don't put in your server name, or your domain name, or your MySQL server name.

say you have a website. it's located at http://whatever.com/html/. say you have a flash version of this same website that uses php as a backend. the php files that flash uses are located at http://whatever.com/flash/. so, you put your URL to the php files that output flash crap instead of using the URL that you would normally browse to in a web browser.