xref
Creates a link to a different location.
The href attribute in the <xref> element provides the location of the target.
You can use the <xref> element to create a link to:
A different topic within the same deliverable.
An external source such as a web page.
A different location within a topic.
Note:
Referencing a location within the same topic might create circular references. When circular references in a publication reach a threshold, the publication might fail to open. Therefore, avoid adding links to content within a topic.
Use relationship tables to create relationship between topics in a document. Use the <xref> element only when necessary. See Cross-reference links in topic for guidance about when to use an xref.