<type name="Magento\Store\App\FrontController\Plugin\DefaultStore">
    <arguments>
        <argument name="runMode" xsi:type="init_parameter">
            Magento\Store\Model\StoreManager::PARAM_RUN_TYPE
        </argument>
        <argument name="scopeCode" xsi:type="init_parameter">
            Magento\Store\Model\StoreManager::PARAM_RUN_CODE
        </argument>
    </arguments>
</type>

This is a type configuration.

This configuration is for the base area. Base area configurations will apply to all the sub-applications.

This configuration tells the Object Manager that when a user wants a Magento\Store\App\FrontController\Plugin\DefaultStore object that the following arguments should be used in the foo object's constructor.

• $runMode = Magento\Store\Model\StoreManager::PARAM_RUN_TYPE;
• $scopeCode = Magento\Store\Model\StoreManager::PARAM_RUN_CODE;

<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.