This sheet contains the default configuration for entire site. If a specific sheet don't has a specific configuration, the default values get picked from this sheet.
This sheet contains the details on all the internal pages of your site. This could be a 'Contact us' page or 'About us' page or any internal page of the site.
This sheet can be used for advanced integrations using external javascripts. Use this sheet when you have an external java script that need to be embedded into site. This sheet can be also used to add css for extra syling.
This sheet can be used as you want. Some usecase could be using this sheet to hold temporary data before you add data to Body-Cards. You can safely ignore using this sheet.