_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.

Use Confluence for technical documentation | Confluence Cloud | Atlassian Support

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

Insert the excerpt macro | Confluence Cloud | Atlassian Support

Add excerpts to a page with the insert excerpt macro | Confluence Cloud | Atlassian Support