The template page can be in any format you want it to be as long as it can process php code. Normally, it must have the .php extension (although you can change the mime types to use something else).
The content will go whereever you have the code to include the file, like inside a table cell etc. Since the entire file is included in one area, it will not work if you want the information to be spread out, like a title in the page header, a blurb on the side nav, AND something in the big blank space.
If that is what you were planning, you might try creating a set a variables for each if/then statement. This snippet would have to go at the top of the template file before you called any of the variables...
<?
if($x=="engineering"){
$titleVar="Engineering Information";
$sideBlurbVar="Engineering is way cool";
$contentIncludeVar="engineering.html";
}elseif($x=="fabrication"){
$titleVar="Fabrication Information";
$sideBlurbVar="Fabrication is even cooler than engineering.";
$contentIncludeVar="fabrication.html";
}
?>
Then, when you want to use a bit of that information, just call it...
<head>
<title><?=$titleVar?></title>
</head>
<body>
Pretend this is a nicely formatted page with a little side bar...
<?=$sideBlurbVar?>
In the center of the page, you want to include the content.
<?
include("$contentIncludeVar");
?>
</body>
