In the Java programming language a resource is a piece of data that can be accessed by the code of an application.[1][2]
An application can access its resources through uniform resource locators, like web resources, but the resources are usually contained within the JAR file(s) of the application.
A resource bundle is a set of key and value pairs, stored as a resource, that is commonly used to allow the localization of an application. For this purpose different resource bundles with a common set of keys are used to store translations for the messages and user interface texts of an application.