Language and geographic environment are two important influences on our culture. They create the system in which we interpret other people and events in our life. They also affect, even define, proper form for presenting ourselves and our thoughts to others. To communicate
effectively with another person, we must consider and use that person’s culture, language, and environment.
Similarly, a software system should respect its users’ language and geographic region to be effective. Language and region form a locale, which represents the target setting and context for localized software. The Java platform uses
java.util.Locale objects to represent locales. This article describes the
Locale object and its implications for programs written for the Java platform.
Have a look. It’s an older article, but still perfectly valid and useful: Understanding Locale in the Java Platform.