I think better explaination could be:
a GSM phone will have IMEI which in trun will only with with a SIM card
a CDMA/iDEN will have ESN and will not have any IMEI on it and will not take SIM card.
8830 Worl phone from Verizon has GSM band but its CDMA phone so it has ESN only.
Never be silent about the things that matter, but what about Democracy? That matters too