Cross-references are index entries that point to related entries, instead of a page number. You create cross-references using the Index panel. Cross-references can serve different purposes in an index:
Cross-references associate common terms with equivalents used in your document or book. For example, Fauna. See Animals. Entries with such cross-references do not contain page references; they simply point to equivalent terms that are indexed more fully.
Cross-references point to other entries related to, but not equivalent to, a topic. For example, Cats. See also Wildcats. In this case, the index entry containing the cross‑reference also contains page numbers and/or subentries that are directly related to the entry’s topic.
When you create a cross-reference in InDesign, you can also select a cross-reference prefix. “See” and “See also” are static text. When you choose “See [also],” InDesign automatically assigns the correct prefix to the cross-reference each time the index is generated:
Entries with page numbers, subentries, or both are given “See also.”
Entries without page numbers or subentries are given “See.”
Using the “See [also]” option frees you from the task of manually updating cross‑references as the contents of your index entries change.
Cross-references appear in the Index panel and the generated index, but are not associated with index markers in the document itself.
Cross-references with “See [also]” appear as “See [also]” in the Index panel; however, the correct prefix will appear in the generated index story.