What is Interop?

Question

I have to make an analysis for an application that generates word documents based on several wizard forms and templates. I should make an estimation for VB6 and C#. In VB6 there is the problem that you cannot reference the word object library because it would not work on other word versions, so you would need to use CreateObject("Word.Application") and always use the object type instead of Document, Field, Bookmark,... which also means no intellisense, context-sensitive-help,... I wander if this is the same in .NET, or if the so-called interop object libraries work on all versions of office (at least office 2000). So during development we just reference this interop lib and at runtime it will just look for the word version installed... I would not use any advanced features. Everything is very basic... I read a few MS KB articles about this but i don't really know what is true. I think they tell me it is possible, but they do not promote the use of interop... Anyone knows why? Greets