<type name="Magento\Framework\App\ResourceConnection">
    <arguments>
        <argument name="connectionFactory" xsi:type="object">
            Magento\Framework\App\ResourceConnection\ConnectionFactory
        </argument>
    </arguments>
</type>

This is a type 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 configuration tells the Object Manager that when a user wants a Magento\Framework\App\ResourceConnection object that the following arguments should be used in the foo object's constructor.

• $connectionFactory = new Magento\Framework\App\ResourceConnection\ConnectionFactory (...)