Template:Documentation
Documentation 
This template adds the documentation of said template page in an easy way. The documentation page of a template is the name of the page, and /doc at the end. So, this would be the Documentation page of the Documentation template.
Usage
Wrap with <noinclude> and tags when you insert this at the end of a template page to inform users about its usage.
It will be replaced with the contents of the /doc page.
For example, the inclusion of this page in Template:Documentation is written:
<noinclude>
{{Documentation}}
</noinclude>