The Luggage defines how your package installer or disk image is built. It provides a series of concrete steps that must be taken to meet dependencies. It lists all of the source files, scripts, and other installer resources explicitly. When the last dependency is met without errors, you’ve got your result.
This means that you, or anyone else on your team if you have one, can review what is being done to create your installers. You can see the source, you can see the actions that will be taken to turn the source into the package, and you get the resulting package or disk image. You can even insert text comments in the makefiles for your Luggage projects, as reminders of why certain actions are taken.
Compared to a workflow using Apple’s graphical PackageMaker tool, the Luggage is much more transparent and open to review. This transparency helps both when you are creating your installer project and also six months later when you — or someone else — needs to revise it.