The language selector itself does nothing more than that: change the language, or to be more precise, change the culture the page should be displayed in.

DotNetNuke does not support dynamic (content) localization out of the box, only static (interface) localization is supported.

Having said that, there are third party modules available that let you localize the content as well. These modules all work essentially the same: they read the current culture (language) from the page, and display content that corresponds to that culture. The edit controls of such module will let you enter content for each available locale in your portal.

If you are looking for multi lingual capable modules, please have a look here: http://www.dotnetnuke.com/tabid/794/action/cat/lcl/2/parentID/104/Default.aspx or here: http://www.snowcovered.com/snowcovered2/Default.aspx?tabid=139&mastercategoryid=16&subcategoryid=68

Cheers,

Erik