<type name="Magento\Framework\App\FrontControllerInterface">
    <plugin name="default_store_setter"
            type="\Magento\Store\App\FrontController\Plugin\DefaultStore"></plugin>
</type>

This is a type configuration.

This configuration is for the adminhtml area. This is the area that corresponds with the Magento admin sub-application.

This configuration also tells the object manager to use the \Magento\Store\App\FrontController\Plugin\DefaultStore plugin class with Magento\Framework\App\FrontControllerInterface objects.