Message catalogs provide a consistent way to access messages such as error messages or user dialogs and are easily created, modified, and accessed. They are separate from the programs that call them, so they are easily modified. For example, translating applications into a native language only requires the message catalog to be translated.
You usually create your own message catalog to output messages from an application; you may use the system error messages if they are appropriate. A special type of message catalog is a HELP catalog. Messages are directly output to you through a predefined interface.
