CMS Made Simple Forums

Hi all ! in sitepreferences one option has been added, i mean 'Default language for the frontend'. what does it mean? is it posibble to have a multilingual site with this feature? if yes how? if (i think) no , what is the advantage of setting this parameter?
Thanks in advance

Edit ---->
finally i find out that setting this parameter will set the language for login page!

Probably it refer to the default lang="" parameter to be used with modules.