Simplify the following text for a Grade 3 native English-speaking person.
Original: ISO 3166-2 is part of the ISO 3166 standard published by the International Organization for Standardization ( ISO ) , and defines codes for the names of the principal subdivisions ( e.g. , provinces or states ) of all countries coded in ISO 3166-1 .
Simplified: ISO 3166-2 is a standard .