A plain-language explanation
Nofollow refers to the way a link is treated, while noindex informs the search engine that a given page should not appear in the index.
Where it helps in practice
Nofollow describes a link relationship while noindex controls page indexing; treating them as interchangeable solves the wrong problem.
The decision before implementation
Decide whether the goal concerns link endorsement or search inclusion and whether a crawler can read the directive.
How to verify the result
Verify response code, robots directives, internal links and index status after recrawling.
