From a merge: This is a redirect from a page that was merged into another page. This redirect was kept in order to preserve the edit history of this page after its content was merged into the content of the target page. Please do not remove the tag that generates this text (unless the need to recreate content on this page has been demonstrated) or delete this page.
For redirects with substantive page histories that did not result from page merges use {{R with history}} instead.
From a related word or phrase: This is a redirect from a word or phrase (term) to a page title that is related in some way. This redirect might be a good search term, or it could be a candidate for a Wiktionary link.
Redirects from related words are not properly redirects from alternative spellings of the same word. They are also different from redirects that are subtopics or related topics, because unlike those, a related word or phrase probably does not warrant its own subtopic section in the target page or possess the possibility of ever becoming an article, template, project page, and so forth.