To an article without mention: This is a redirect to an article without any mention of the redirected word or phrase.
For titles that are obvious omissions from target articles, check the rcat index for more specific templates to use instead of this rcat – examples: {{R from misspelling}} for misspellings of article titles or {{R from incorrect name}} for wrong names.
To a related topic: This is a redirect to an article about a similar topic.
Redirects from related topics are different than redirects from related words, because a related topic is more likely to warrant a full and detailed description in the target article. If this redirect's subject is notable, then also tag it with {{R with possibilities}} and {{R printworthy}}.