This page is an essay, containing the advice or opinions of one or more Wikipedia contributors. Essays are notWikipedia policies or guidelines. Some essays represent widespread norms; others only represent minority viewpoints.
On Wikipedia, relevance is a consideration whether a fact or detail in an article is useful to the reader or is out of scope of the article. If a fact is not relevant to the topic of the article, it should not be mentioned in that article. This does not mean it can not be mentioned in some other article. Mentioning things that are irrelevant to an article's topic can unnecessarily bloat an article, making it difficult for a reader to remain focused, and can also give the things mentioned undue weight.
Directness of relevance is an important measure and consideration. The highest relevance is information directly about the topic of the article. "John Smith is a member of the XYZ organization" in the "John Smith" article is an example of this. Information that is "one step removed" is less directly relevant, should receive a higher level of scrutiny before including, but may still may be sufficiently relevant for inclusion. For example, criticism of John Smith is information about what others feel about John Smith. So is information about the XYZ organization. Information that is "two steps removed" should usually not be included. For example "Murderer Larry Jones was also a member of the XYZ organization".