In order to create a multi-language Magento 2 store you need to add a new store view by going to Admin Panel Stores > All Stores and pressing the Create Store View button.

Magento 2 Multi-Language Store,Create Website

Store View Information

1. Choose store the store-view will be linked to in Store select box.

2. In the Name field, you correspondingly set the name of the store-view.

3. Set the code of the store-view (it can be used in the URL).

3. Enable the store-view in Status select box.

Magento 2 Multi-Language Store,Store View Information

Once you have finished with all the changes don't forget to press the Save Store View button.

Magento 2 Multi-Language Store,Store View Information

Edit Store-view

Also, you can edit store-views, e.g. change the name of a store view. You can do this by clicking on store-view link and editing its fields easily, just like during the creation.

Magento 2 Multi-Language Store,Store View Information

Set Locale (Set Language)

Once creating a new store view has been done, you have to set it's locale by going to Admin Panel > Stores > Configuration > Store View > [Store View Name].

Magento 2 Multi-Language Store,Store View Configuration

In the General section find Locale Options and set a language for the store view.

Magento 2 Store View Configuration,Locale Options

Once you have finished with the store view locale configurations don't forget to press the Save Config button.

Magento 2 Configurations,Save Config

After all these actions you should reindex Magento 2 and clear the cache.