From Rosetta Code

This is a semantic property.

Properties describe semantic characteristics of Rosetta Code pages, typically determined automatically from other features described in the page such as which templates are used.

To use this template, add {{property}} to the page. If the property is not linking pages, add {{property|type}}; for example, if it is a boolean property, type should be Boolean.

This is a template. There are many others. See Category:RCTemplates for a complete list of templates.