Artifactory config descriptor is the file artifactory.config.latest.xml located under $JFROG_HOME/etc/artifactory.
This xml file follows the xsd schema file defined at the top of it. Having a corrupted config descriptor will cause artifactory to fail to come up. You might be having a corrupted config descriptor for many reasons, but it usually happens after a failed upgrade, rollback, import, or config descriptor bootstrap.
A working config descriptor file needs to have the correct xsd version that matches the running artifactory version, but it also need all the properties in it to be valid according to the xsd schema.