<virtualType name="Magento\Theme\Model\Layout\Config\Data"
             type="Magento\Framework\Config\Data">
    <arguments>
        <argument name="reader" xsi:type="object">
            Magento\Theme\Model\Layout\Config\Reader\Proxy
        </argument>
        <argument name="cacheId" xsi:type="string">
            page_layouts_config
        </argument>
    </arguments>
</virtualType>

This is a virtual type configuration.

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

This virtualType configuration tells the Object Manager when a user wants a virtual Magento\Theme\Model\Layout\Config\Data object that it should return a Magento\Framework\Config\Data object.

This configuration tells the Object Manager that when a user wants a Magento\Theme\Model\Layout\Config\Data object that the following arguments should be used in the foo object's constructor.

• $reader = new Magento\Theme\Model\Layout\Config\Reader\Proxy (...)
• $cacheId = "page_layouts_config";

<virtualType name="Magento\Framework\View\Layout\PageType\Config\Data"
             type="Magento\Framework\Config\Data">
    <arguments>
        <argument name="reader" xsi:type="object">
            Magento\Framework\View\Layout\PageType\Config\Reader
        </argument>
        <argument name="cacheId" xsi:type="string">
            page_types_config
        </argument>
    </arguments>
</virtualType>

This is a virtual 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 virtualType configuration tells the Object Manager when a user wants a virtual Magento\Framework\View\Layout\PageType\Config\Data object that it should return a Magento\Framework\Config\Data object.

This configuration tells the Object Manager that when a user wants a Magento\Framework\View\Layout\PageType\Config\Data object that the following arguments should be used in the foo object's constructor.

• $reader = new Magento\Framework\View\Layout\PageType\Config\Reader (...)
• $cacheId = "page_types_config";

<virtualType name="SectionInvalidationConfigData"
             type="Magento\Framework\Config\Data">
    <arguments>
        <argument name="reader" xsi:type="object">
            SectionInvalidationConfigReader
        </argument>
        <argument name="cacheId" xsi:type="string">
            sections_invalidation_config
        </argument>
    </arguments>
</virtualType>

This is a virtual type configuration.

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

This virtualType configuration tells the Object Manager when a user wants a virtual SectionInvalidationConfigData object that it should return a Magento\Framework\Config\Data object.

This configuration tells the Object Manager that when a user wants a SectionInvalidationConfigData object that the following arguments should be used in the foo object's constructor.

• $reader = new SectionInvalidationConfigReader (...)
• $cacheId = "sections_invalidation_config";

<virtualType name="pdfConfigDataStorage"
             type="Magento\Framework\Config\Data">
    <arguments>
        <argument name="reader" xsi:type="object">
            Magento\Sales\Model\Order\Pdf\Config\Reader
        </argument>
        <argument name="cacheId" xsi:type="string">
            sales_pdf_config
        </argument>
    </arguments>
</virtualType>

This is a virtual type configuration.

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

This virtualType configuration tells the Object Manager when a user wants a virtual pdfConfigDataStorage object that it should return a Magento\Framework\Config\Data object.

This configuration tells the Object Manager that when a user wants a pdfConfigDataStorage object that the following arguments should be used in the foo object's constructor.

• $reader = new Magento\Sales\Model\Order\Pdf\Config\Reader (...)
• $cacheId = "sales_pdf_config";

<virtualType name="Magento\Payment\Model\Config\Data"
             type="Magento\Framework\Config\Data">
    <arguments>
        <argument name="reader" xsi:type="object">
            Magento\Payment\Model\Config\Reader\Proxy
        </argument>
        <argument name="cacheId" xsi:type="string">
            payment_config
        </argument>
    </arguments>
</virtualType>

This is a virtual type configuration.

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

This virtualType configuration tells the Object Manager when a user wants a virtual Magento\Payment\Model\Config\Data object that it should return a Magento\Framework\Config\Data object.

This configuration tells the Object Manager that when a user wants a Magento\Payment\Model\Config\Data object that the following arguments should be used in the foo object's constructor.

• $reader = new Magento\Payment\Model\Config\Reader\Proxy (...)
• $cacheId = "payment_config";