Well, on that site.. it's like this..
category1 = purple template
category2 = pink template
It's not doing anything special, just changing colors..
same thing as putting
$category = "5"; //just a number I used... means nothing
$template = "purple"; //just a color the template is named..
include ('path/to/show_news.php');
if you mean how can you put different templates on one page at the same time, my answer is that if you can put more than 1 category on a page, you use the same thing $template = "whatever"; .. but I've never used 2 templates at the same time.