Country Codes

ISO 3166 is a standard published by the International Organization for Standardization (ISO) that defines codes for the names of countries, dependent territories, and special areas of geographical interest. ISO 3166 has several parts, including ISO 3166-1, which defines the two-letter (ISO 3166-1 alpha-2) and three-letter (ISO 3166-1 alpha-3) country codes, and ISO 3166-2 which defines subdivision region codes within a country.

• ISO 3166-1 alpha-2 codes: These are two-letter country codes used to represent countries and territories. For example, the alpha-2 code for the United States is "US," and for Canada, it's "CA".
• ISO 3166-1 alpha-3 codes: These are three-letter country codes also used to represent countries and territories. For the United States, the alpha-3 code is "USA", and for Canada, it's "CAN".
• ISO 4217 Currency codes:Currency codes are standardized three-letter codes that are used to represent and identify currencies in international finance, trade, and commerce. ISO 4217 defines not only the currency codes but also the numeric codes and the names of currencies. For example, the currency code for the USA is "USD" and for Canada, it's "CAD".
• International telephone codes: International dialing codes are numerical prefixes used to indicate a specific country or region when dialing a phone number from one country to another. These codes are an essential part of the international numbering plan, which helps ensure that calls are routed correctly to the destination country or region. International telephone codes are often referred to as International Direct Dialing (IDD) codes.

These codes are widely used in various international contexts, including domain names (e.g., .us for the United States), vehicle registration codes, and international shipping labels, among other applications, to uniquely identify countries and territories.