Currency codes are three-letter abbreviations used to represent different currencies around the world. These codes are standardized by the International Organization for Standardization (ISO) and are part of the ISO 4217 standard. For example, the currency code for the United States Dollar is USD, while the code for the Euro is EUR. These codes help facilitate international trade and financial transactions by providing a clear and concise way to identify currencies. They are commonly used in banking, travel, and online shopping, ensuring that everyone understands which currency is being referred to in a transaction.