In computing, a locale is a set of parameters that defines the user's language, country and any special variant preferences that the user wants to see in their user interface. Usually a locale identifier consists of at least a language identifier and a region identifier.
On POSIX platforms such as Unix, Linux and others, locale identifiers are defined similar to the BCP 47 definition of language tags, but the locale variant modifier is defined differently, and the character set is included as a part of the identifier. It is defined in this format: ]. (For example, Australian English using the UTF-8 encoding is en_AU.UTF-8.)
Read more about Locale: General Locale Settings, Programming and Markup Language Support, POSIX Platforms, Specifics For Microsoft Platforms