Example on one order framework using Guid and ref_guid on table level

Hi Forum,

I am new to CRM can someone explain me the one order framework in header and item level tables with an example. I am unable to figure out what is the difference. crmd_orderadm_h and crmd_orderadm_i tables how do we connect them in which field and how is GUID and REF_GUID Related.

Thanks in Advance

Mathew Hayden.