Transposer is a plugin for Carrara that allows for importing not only the objects and their textures, but their animation as well. The nice thing about Transposer is, if you make changes to the file in Poser, and then open your carrara file again, it will automatically bring over the changes made, without having to redo all that work manually. But, your right, Transposer is not needed to get the files over. It just is a manual thing as opposed to an automatic thing.