Hi sai,
There is no diffrence between Business unit and org unit,in GRC 5.3 called as Business unit and come down to GRC 10.0 called Organization unit,in 10.0 basically we create Root organization,under root organization we will create child oraganization(nothing but business units)you will define child org's based upon your client requirement.
why this child oraganizations required is,when creation of mitigation controle ids it will ask for organization unit(nothing but business unit) you will define diffrent mitigation controles for different business process.It shold be easy to idetifying for your customer....
Regards
Ravikumar.ch
