Translating in Drupal 8
Drupal 8 wouldn't be Drupal 8 if it didn't change translation as it changes everything else. The Drupal 8 Multilingual Initiative, under the lead of Gábor Hojtsy, did a great job and reworked nearly everything that was related to translation.
In Drupal 8, there are 4 main pillars for translation:
Language: This is the base service for all modules that deal with data on your site. Even if you don't actually use translation features, it manages languages wherever you may need them on your site or within your modules. Additionally, it is responsible for language detection and selecting the correct language in which to deliver your translated content and configuration.
Interface: The interface component supports translation of Drupal itself, as it provides all the tools to translate the interface strings (as they were known in previous versions).
Content: In contrast to Drupal 7's Content translation module, this handles the translation of all fields for all defined entities...
