Notification
Notification is an Amiga facility whereby an application may be informed whenever a change is made to a file of interest. Through notification it is possible for an application to find out whenever the user has made a change to any preferences data file. This allows the application to make an adjustment to reflect the new preferences settings. See Chapter 11 for more information.
Notification can be used to let your program know when the user makes changes [with] a system-wide preference editor.
Since an application has to handle its own preferences, there is not much point in getting notification about changes to application preferences files. However, changes to system preferences files may be relevant. For instance, a publishing program may want to be notified whenever the user changes the printer graphic setting from black-and-white to colour.
Notification is a new facility in Release 2 of the Amiga operating system. Under previous versions of the operating system, an application could ask Intuition to send it a message whenever system preferences data changed. This method still works for Preferences items that existed under Release 1.3.
In either case, the important thing to understand is that your application is not expected to respond to every change made to system preferences. This is an extra feature you may add to your application if you believe it is warranted.