Multilingual modules

1) Locale (Interface Translation) module
Located at core/modules/locale/locale.module

Translates the built-in user interface, your added modules and themes.

Automated downloads & updates
Protected local translations
English customizable/removable, no more need english default language
Built-in translation UI revamped for easier editing
Plural version editable on an integrated interface
Protected custom translations, exportable
English text, customizable

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2) Content Translation module
Located at core/modules/content_translation/content_translation.module

Allows users to translate content entities.
Allows you to translate your site content, including pages, taxonomy terms, blocks, etc., into different languages.

Field-level configurability
Applies to all content
Views integrated
Exposed language information via search API
Per-language content access

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3) Configuration Translation
Located at core/modules/config_translation/config_translation.module

Provides a translation interface for configuration.
Allows you to translate text that is part of the configuration, such as field labels, the text used in Views, etc.

All configuration is translatable (roles, text formats, blocks, views, panels, etc.)
Built-in responsive translation interface
All shipped are pre-translatable on localize.drupal.org