Hi Hari,
You are right in concept. A country group is a set of countries which we can put together and which have a same regulation requirement. As Dhilipan pointed out, this is mostly used in the case of SPL as they don't have much difference. It may be licensing related country group also but you need to make sure that all those countries follow the same adherence to regulations and there is no difference between them. Any such valid difference will make them non eligible to be clubbed and we should be extra cautious to use them in a country group.
I hope you got it now.
Regards,
Aman