A map's canvas is 0 0 width height, viewBox says so, and a region's path is M x,y L x,y … Z with one piece for each part (an island is a piece), to two decimals. A region's code is its ISO 3166-1 alpha-2 code on the world, and on a country's regions the code Natural Earth gives (a postal code, the ISO 3166-2 part, or a number), or the prefecture number in Japan. On a country's regions, iso is the full ISO 3166-2 code (CA-ON), the one kuni has: see ISO codes below. neighbors lists the regions that share a border point with it. group is the continent on the world and the larger part of the country on a map of regions, and is what quiz distractors use.
Every region of a country carries iso, its ISO 3166-2 code from kuni, the current one where Natural Earth's is out of date (Paris is FR-75C, Silesia PL-24); where Natural Earth draws one ISO subdivision as several regions, each carries the code of the one it lies in (County Dublin's four councils are all IE-D). docs/iso-codes.md says how each code is chosen. Norway's counties, drawn as they were before 2020, carry the codes of the counties of 2024 they lie in. 7 of the 1,342 regions have no code: a county split since (Northamptonshire), a territory with none (Jervis Bay), and a few more. docs/iso-codes.md lists every one with the reason.
A region that is exactly one ISO subdivision takes kuni's names, so a map and a form name a place alike. The rest keep Natural Earth's names, and no two regions of one map share a name in either language. docs/names.md lists every name the map prints that is not kuni's, with the reason.