If you would like to use a metadata definition called "Top news" for the e.g. five news archives you have on a web site you normally add the definition on each of the five different news archives. If you instead add the definition for the news page template the metadata definition is there for each and every page created out of the news template.
Metadata (Site) is commonly used if a metadata definition needs to be mandatory for a certain template. You add the definitions for metadata (site) the same way you add ordinary metadata:

You need to switch to template mode, choose desired template and select Properties. Beneath the tab Metadata field, you can choose to either apply the metadata definition on pages, files, and/or layouts.
In order to activate the metadata definition on pages, click the plus sign to the right of Metadata fields applied on pages based on this template.



