The "callingParty" is always the calling number. When you have a telephone and you make a call, this is your number of the phone.
The "callingPartyName" can be either the calling number or the calling name or nothing. Which option is selected, depends on how the telephony system (e.g. CUCM) is configured.
E.g. if no calling name is configured, then it probably will automatically be the calling number.