ISO 639 is a set of international standards that defines codes for the names of languages. It is maintained by the International Organization for Standardization (ISO) and consists of several parts, each providing different types of language codes. The most commonly used parts are ISO 639-1, which includes two-letter codes, and ISO 639-2, which features three-letter codes. These codes help in the identification and classification of languages in various applications, such as software localization, library cataloging, and linguistic research. By standardizing language codes, ISO 639 facilitates communication and data exchange across different languages and cultures.