<type name="Magento\Eav\Model\TypeLocator">
    <arguments>
        <argument name="typeLocators" xsi:type="array">
            <item name="simpleType" sortOrder="50" xsi:type="object">
                Magento\Eav\Model\TypeLocator\SimpleType
            </item>
            <item name="complexType" sortOrder="10" xsi:type="object">
                Magento\Eav\Model\TypeLocator\ComplexType
            </item>
            <item name="serviceClassType"
                  sortOrder="0"
                  xsi:type="object">
                Magento\Eav\Model\TypeLocator\ServiceClassLocator
            </item>
        </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\Eav\Model\TypeLocator object that the following arguments should be used in the foo object's constructor.

• $typeLocators = [...items...];

<preference for="Magento\Framework\Webapi\CustomAttributeTypeLocatorInterface"
            type="Magento\Eav\Model\TypeLocator"></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\Webapi\CustomAttributeTypeLocatorInterface object that it should return a Magento\Eav\Model\TypeLocator object.