Help:Template
Templates are pages that can be included into other pages, to produce standardized layouts, complicated structures and so on. MediaWiki reserves one namespace for them. Each template page has the prefix Template:. Templates can also manage categories for pages.
Examples
simple templates
{{dead link}}- Template:dead link
templates with arguments
{{external image}}- Template:external image{{Infobox Interval}}- Template:Infobox Interval