"When citizen developers design and implement applications using APP Studio, they typically include multiple discrete components of functionality. As those citizen developers become more familiar with the business needs of the organization, opportunities to reuse those components in other applications may arise.
To create reusable built-on applications and components from citizen developer built application..."
Also, some of this page seems to lack context.
An example: "At the point that all dependencies on the current application have been removed, the Refactoring Wizard (System > Refactor > Classes) can be used to remove “-APP-“ from the case type’s class name. This refactored case type can then be placed within its own application. The original application then defines the new component application as a built on application. Lastly the case type rule within the original application must be restored. This can be accomplished by performing a “bottom up” Save-As for the refactored case type rule to its parent application."
.....there is no context for the -APP- component in the class name as the class name is never given in the page. Also, since the application structure really isn't given in the page, it's easy to get lost in the final part in bold, above.
@DENNISYOUNG Here is the corrected text concerning creating a new component application:
At the point that all dependencies on the current application have been removed, the Refactoring Wizard (DEV Studio > Configure > System > Refactor > Classes) can be used to rename the original class by replacing the existing application reference in the original case type’s class name “-APP-“ with the name of a the new component application “-NEWAPP-“. This newly created and refactored case type class and all its associated rules can then be placed within its own component application with the name NEWAPP. The original application is then modified to reference the new NEWAPP component application as a built on application. Finally, the original case type class from the original application is re-created by importing it as a direct descendant of the newly created and refactored class in the NEWAPP component application. When re-created by importing, the original case type class is automatically saved to the original application's application ruleset.