When used by itself:

From an identifier: This is a redirect from a unique (alpha-)numerical identifier (like an EAN) to an article discussing that particular class of identifiers in mainspace. By convention the redirect must include the parenthetical disambiguator "(identifier)". Its purpose is to avoid clutter in "What links here" of the target article and to improve reverse lookup of articles containing references to individual manifestations of this particular class of identifiers (typically linked to through templates (of the various , , and similar types) but it can also be used directly in piped links naming such manifestations), so that all mentionings of this class of identifier can be found in articles more easily. Do not use this redirect for "normal" links to the target page (in many cases, a similarly named redirect without the "(identifier)" disambiguator exists for this purpose).