The term localization usually refers to the process of translating the text in the UI to the "local" language of a target user audience that is different from the language of the primary version or first release.
The first release of World of Warcraft used the English language for a North American (US) user audience.
|Country||Language||Locale Code||Official Website|
|Republic of Korea||Korean||
|United Kingdom of Great Britain and Northern Ireland||English||
|United States of America||English||