<preference for="Magento\Framework\App\ScopeResolverInterface"
            type="Magento\Framework\App\ScopeResolver"></preference>

This is a preference configuration.

This configuration is the application level configuration (`app/etc/di.xml`) fo the object manager. It is not a part of a specific module, but will apply to all sub-applications in Magento 2 (cart, admin, api, cron, etc).

This preference configuration tells the Object Manager when a user wants a Magento\Framework\App\ScopeResolverInterface object that it should return a Magento\Framework\App\ScopeResolver object.

<preference for="Magento\Framework\App\ScopeResolverInterface"
            type="Magento\Store\Model\Resolver\Store"></preference>

This is a preference configuration.

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

This preference configuration tells the Object Manager when a user wants a Magento\Framework\App\ScopeResolverInterface object that it should return a Magento\Store\Model\Resolver\Store object.