{{Documentation}} is a meta template used on all template pages to document how the template is used. The documentation is displayed in a green box like you are seeing now and automatically loads the content from a /doc subpage.
Usage
This template is typically placed at the top of the template code with no space before <noinclude> (which would cause extra space on pages where the template is used).
<noinclude>{{Documentation}}
</noinclude>
Categorization
Categories that apply to the template itself should be added to the bottom of the /doc subpage inside <includeonly>...</includeonly>.
This template adds pages that have {{Documentation}} but no /doc subpage (and therefore no actual documentation) to Category:Templates missing documentation.
Linked templates
The final header is Templates that use this template. There you will find a list of all template that use this template, allowing for easier visibility of the impacts
Technical notes
- Use of this template allows the template page to be protected where necessary, while allowing anyone to edit the documentation and categories.
- If the documentation page contains <noinclude> or <includeonly> tags as part of the visible documentation text, replace the
<with&<.
See also
Wikipedia:Template:Documentation - The Wikipedia documentation template.