From Wikigogy

This template example shows how templates work. See also http://MediaWiki.org/wiki/Help:Templates

includeonly

this

<includeonly>
Stuff in here will show in, be "included only" in, the pages that use the template. It does not 
show in the master template, except when you are editing the master template wiki text. This 
might be useful to connect the pages using the template to a [[category]] without connecting the 
template itself to that category.
</includeonly>

gives you this

noinclude

this

<noinclude>
Stuff in here will show in the master template but will not show in the pages that use the template. 
This is useful for putting instructions on how to use the template, right on the template page.
</noinclude>

gives you this

Stuff in here will show in the master template but will not show in the pages that use the template. This is useful for putting instructions on how to use the template, right on the template page.

Parameters

Templates can use parameters.