The CMS Joomla! supports many different languages in the frontend and backend applications already. Since Joomla! 1.5 the articles also do have a language parameter which allows to identify the language in which an article is written. However all other information such as section/category descriptions, module content or menu names do not have such a tag. This tag will the improve the possibilities of extensions to sort out language specific content. E.g. a RSS feed extension can present information for different languages or a content list can present the number of articles in one specific language without complex and time intensive database queries over a 'text' type filed.
The idea of this change is described and discussed in the following threads: