Difference between Arguments and CustomActionData in VS CustomAction

Question

In a Visual Studio 2008 setup project, what is the difference between the two properties: Arguments and CustomActionData?

In the descriptions that I've read on MSDN, they sound about the same. When should a person use one vs the other.
http://msdn.microsoft.com/en-us/library/kyd017kk%28VS.80%29.aspx

Thanks,

Neal