The locale code can have between one and three elements as follows: [lang]_[country].[encoding]. The [lang] part is defined by iso 691-1 or iso 639-2 and has two or three characters. The [country] part is normally two capital letters and is defined by iso 3166. The [encoding] part can be ‘utf-8‘, ‘iso-8859-1′ etc.
Different operating systems use different codes for language and country and (in the case of windows) for the encoding. Even between versions of Linux there are differences. This is the reason that a list of codes can be used — one of them might be known by the specific host. It is worthwhile looking up the codes used by openBSD, suse, redhat, windows etc. (a real jungle 
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