<preference for="Magento\MediaContentApi\Model\SearchPatternConfigInterface"
            type="Magento\MediaContent\Model\Content\SearchPatternConfig"></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\MediaContentApi\Model\SearchPatternConfigInterface object that it should return a Magento\MediaContent\Model\Content\SearchPatternConfig object.