ResourceBundle is a property file handler with locales 
support, it allows you to support multiple languages in 
your application. There's a full explaination on what 
ResourceBundle is and how it has to be used in the javadoc.

Yes, ResourceBundle can be used instead of the Properties 
class. It would be particularly usefull when developing 
applications for different languages. The ResourceBundle 
class will find the correct properties file based on the 
current user locale.

The advantages of using ResourceBundle taken from the 
javadoc This allows you to write programs that can: 

be easily localized, or translated, into different 
languages 
handle multiple locales at once 
be easily modified later to support even more locales

resource bundle is to save the message as key value pairs