EDIT 2: I am planning to implement a language switcher, but I don't have a clear understanding of how interface translation works in WordPress out-of-the-box, without multilanguage plugins (I don't need a full multilanguage solution). I know about portable objects localization and I want to make those translations available for the users both in the back-end and the front-end.
EDIT: I'm not talking about content translation (pages, posts, etc.), only interface strings.
I have some questions about the translation of both the back-end and the front-end of WordPress.
Many plugins and themes are shipped with .po/.mo translations, but can the user enable a different language for the front-end interface without using a multilanguage plugin like WPML or Polylang, that use their own language switchers?
Is there some kind of automatic language switching method for the front-end (based on browser, IP, etc.)? As for logged-in users, does the Your Profile language setting affect only the back-end or also the front-end?