The schema guide gives some detail on this, is there more you are looking for?

http://www.cisco.com/en/US/docs/voice_ip_comm/cust_contact/contact_center/icm_enterprise/icm_enterprise_8_5/reference/guide/icm85schema.pdf

I think you'd be interested in page 477 onward?

I'm not in a system now, but I believe if you're in Script Editor itself and viewing the skill group table, if you hit help there it gives you additional information.