Because the name, Interop Forms Toolkit 2.0, really doesn't tell you anything about it, I'd re-name it the "How to extend an established VB6 application with .NET code Toolkit". Yeah, my title might be a bit wordy and all but at least you'd know what it does!
The goal is simple, provide a path to VB 2005 for VB6 developers without requiring them to completely rewrite their VB6 applications. There are plenty of VB6 applications out there that are still working exactly as they were designed. The problem arises when new features are requested or required. Do you continue to enhance a VB6 codebase? Wouldn't be nice to just rewrite the entire app in VB 2005? Unfortunately the rewrite path requires time and money. Even if you decide to rewrite and vow to keep things simple by just bringing the VB6 application over to VB 2005 as it currently is, feature for feature, you end up consuming plenty of resources to create an application that does exactly what the old one did. Sure, you gain the knowledge of knowing you've migrated to the latest and greatest development platform, but typically management doesn't go for the moving for the sake of moving argument.
Taken from the Interop Forms Toolkit page on MSDN this pretty much sums it up:
"The Interop Forms Toolkit provides tools and components that simplify the process of building forms and controls with Visual Basic .NET that can be easily consumed from Visual Basic 6."
Now you have one less excuse as a VB6 programmer to start making the migration to VB 2005. :-)