_ConfluenceInclusions

The Inclusions Library is used to hold content that's specifically for re-use. 

The inclusions library isn't a specific feature of Confluence; the pages in the Inclusions Library are just like any other Confluence page. This is just a technique to use as a place to store content that's specifically for re-use.

https://support.atlassian.com/confluence-cloud/docs/use-confluence-for-technical-documentation/

This technique also makes use of the ‘excerpt macro’ and ‘insert excerpt macro’ features.

https://support.atlassian.com/confluence-cloud/docs/insert-the-excerpt-macro/

https://support.atlassian.com/confluence-cloud/docs/insert-the-excerpt-include-macro/