Please refer to the following URL to know the differences between CCW and RCW,http://onlydifferencefaqs.blogspot.in/2012/07/net-framework-difference-faqs-1_11.html
CCW - COM Callable Wrapper where the dlls which creted using .NET environment and using this COM to VB or other applications.
RCW - Runtime Callable Warapper where the dlls created in any prior version of .net like VB6 and adding those DLLs to .NET environment using add reference and some other import options.
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Jollykid
ccw is called com callable wrapper where as rcw is called as runtime callable wrapper.