Original: ISO 3166-1 alpha-3 codes are three-letter country codes defined in ISO 3166-1, part of the ISO 3166 standard published by the International Organization for Standardization (ISO), to represent countries, dependent territories, and special areas of geographical interest.
Simplified: ISO 3166-1 alpha-3 codes are three-letter country codes in the ISO 3166-1 standard to represent countries and dependent territories. They are published by the International Organization for Standardization (ISO) as part of its ISO 3166 standard.