PHP is a special program that runs on servers (like Arwen's). It takes a look at the web pages' HTML code _before_ it sends it to you. (Hence Hypertext (from HTML) Preprocessor (processes before you see it).
It's useful because it can also save things to the server. With normal HTML this forum couldn't exist, because there's no way for the server to remember your post. PHP allows people to write scripts like this forum, which saves what you post (duh

) so other people can see it too. PHP also lets you do things like password protection (ie the forum's login), counters, tag boards, etc.
PHP can also be used to make the webmaster's job a little easier. You can put a bit of PHP code into a page to make it include other pages... for instance the top of A-U is always the same, no matter what page you're on. Arwen could use a PHP include to include a seperate file with the header. Then she would only have to change that one file, and the change would show up on every page.
PHP is also what drives most of the galleries. instead of Arwen having to copy and paste the (HTML) code for each image, and then go through changing the URLs, she has a PHP script which looks through the images folder and pulls out all the pictures and displays them...automatically.
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<img src="http://thulcandra.com/randombanner/banner.php" title="Banner by Arwen">
I can help with HTML/CSS/JavaScript/PHP/ASP. I can't do graphics or layouts.
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