MediaWiki:Architecture of SAR service
Items & properties
Items and properties are core to wikibase. They operate like a very flexible database. The SAR service relies on some information being properly entered. See Item:Q102 for an example.
Templates
Templates are a MediaWiki system that allow filling text modularly. There is extensive documentation on the MediaWiki docs.
Note that templates can be used from within gadgets (see below) as well as regular pages.