When you tap on the module, M will ask if you'd like to auto-translate all the messages you receive from that friend in the future. You'll have to opt into auto-translation for every conversation, but you can also opt out anytime, say when you're finally fluent enough in Spanish that you don't need help reading it anymore. While the feature is still pretty limited, Facebook plans to expand its capabilities so that it can also translate other languages and can be released in other countries. The social network believes it will enable people to connect in a way that's seamless and natural -- it's definitely much easier to switch on auto-translate than to jump between Messenger and a translator app again and again.