Modifies the normal links in the language selection block in the drop-down menu. Can be used with the module Language Icons, then in the drop-down menu will not only names or language codes, but also flags that very clearly.
Adavnced module that helps to translate Drupal site to the different language. i18n - is a packege with several modules that works with different entities, have additional functions to activate or not if not need.
Interantionalization works with nodes, lables, taxonomy terms, menus, strings and even variables.
Also there are many oter modules that expand possibilities of Internationalization and can translate paths, Views or Profiles.