A plain-language explanation
Nofollow is the value of the rel attribute on a link that signals to the search engine that the link should not be treated as a standard recommendation of the landing page.
Where it helps in practice
Nofollow signals that a link should not be treated as a standard endorsement and is not a way to hide the destination from search.
The decision before implementation
Apply it according to relationship and trust, using sponsored or ugc when those values are more accurate.
How to verify the result
Inspect generated rel attributes, automation rules and whether important navigation was marked accidentally.
