The countryGroup is a list of one or more countries used on many places if the given information is valid for one or more countries. One country can exist in more than one Group.
All countries used must be listed at: validCountries (Header)

country is used in:

B2BCatalogAddress
B2BCatalogContactInfoMatching
B2BCatalogCountries
B2BCatalogCountryGroups
B2BCatalogCountryGroupIds

The two-digit country code is defined according to ISO 3166-1 ALPHA-2. Also see http://en.wikipedia.org/wiki/ISO_3166_Code List

The countryGroupId is referencing to an existing countryGroup.
countryGroupId is used in

b2bOpticLensCatalog→header→supplier→contactInfos→contactInfo→matching b2bOpticLensCatalog→header→subSupplier→contactInfos→contactInfo→matching b2bOpticLensCatalog→header→pricefields→pricefield→matching

The code for the language version is defined according to ISO 639-1 Alpha-2. Also see http://en.wikipedia.org/wiki/ISO_639