Can i get WTObject description?

Hi i'm SeonHo

i looking for description about WTObject
when i configure access control there are display many types
like AbstractWorkPackage, BACTarget, BusinessRule, RootFolder, SubFolder, etc...
But I can not know what each type means.
so i want document that descript Windchill types(type under WTObject in a access rule)
could you please give me a that?

thanks