Use it in questions about adapting software to different languages, regional differences, and requirements of a target market (locale).
In computing, internationalization and localization are means of adapting computer software to different languages, regional differences and technical requirements of a target market (locale).
Internationalization is the process of designing a software application so that it can potentially be adapted to various languages and regions without engineering changes.
Localization is the process of adapting internationalized software for a specific region or language by adding locale-specific components and translating text. Localization (which is potentially performed multiple times, for different locales) uses the infrastructure or flexibility provided by internationalization (which is ideally performed only once, or as an integral part of ongoing development)