For a list of all see Template:Templates.
Templates are used to duplicate the same content across more than one page, reducing maintenance and work needed on creating and updating pages. Changing a template in one place will immediately apply the changes to all the pages that use it.
Due to the amount of traffic and the game being controversial, template creation requires additional permission on top of registered and verified users. For more information on templates, check out Wikipedia's template page or Wikimedia's template page.