I found some information about this on Scott Hanselmans Blog
Does anybody exactly know what this mean?
Is this only for the Office Primary Interop Assemblies, or can I also use this to Embed my Redemption library or other COM libraries?
The process described in Scott Hanselman's blog is called Type Equivalence, a rather nebulous term for the CLR 4.0's support for COM interop type assemblies. Although I haven't had a chance to look at it, there is a video here at Channel 9 that discusses it:
Raja Krishnaswamy and Vance Morrison: CLR 4 - Inside Type Equivalence
http://channel9.msdn.com/shows/Going+Deep/Raja-Krishnaswamy-and-Vance-Morrison-CLR-4-Inside-Type-Equivalence/
Apparently you can write your own "type equivalence" assemblies, and embed them. Note that this probably does not apply to just any COM assembly; type equivalence assemblies implement an interface called IApplication. See here:
Advances in .NET Type system: Type Equivalence Demo http://blogs.msdn.com/mshneer/archive/2008/10/28/advances-in-net-type-system-type-equivalence-demo.aspx