The “Stage EDW Data” Framework Application is identified by ApplicationID 2. If you recall, ApplicationID 2 is mapped to PackageIDs 4, 5, and 6 (LoadWidgetsFlatFile.dtsx, LoadSalesFlatFile.dtsx, and ArchiveFile.dtsx) in the ApplicationPackages table shown above.
The cardinality between Framework Applications and Framework Packages is many-to-many. We see an Application can contain many Packages. The less-obvious part of the relationship is represented in this example: a single Package can participate in multiple Applications or even in the same Application more than once. Hence the need for a table that resolves this many-to-many relationship. I hope this helps explain why Application Package is the core object of our SSIS Frameworks.
Read on for the rest of the story.