That document is simply for the NIF plugin for Blender, not for NIFskope itself, so is assuming you're already familiar with the terms. Open source stuff like this is often notoriously badly documented. A lot of the functions in NIFskope are defunct, never used, or only used internally, which is why there's is little information about them out there. For some of them, I don't think anybody really knows what they do. NIFskope isn't really a modding tool per se, it's more used for editing models that were created in a proper modelling studio, exported to NIF format, and then getting them into a Gamebryo-based engine game like Fallout or Skyrim.
Have you tried the site below? It's not perfect, but slightly better than the one you linked to and at least gives some working examples and is the best source I've found for this in relation to Bethesda games.
https://wiki.beyondskyrim.org/wiki/Arcane_University:NIF_Data_Format#Shader_types
If you want to get into modding at this level, you really need to know some stuff about how meshes, materials, and rendering pipelines actually work: not stuff that's specific to certain games or even NIFskope itself, I mean generic knowledge that's required for all 3D modelling. If you learn, for example, how to create a model from scratch along with its associated materials in something like Blender or Max first, then most of the options in NIFskope should already make some kind of sense. I suggest you look up the terms you're struggling with directly and do some general reading on the topic rather than looking for information related to a specific tool or game engine. There's loads of documentation out there for things like shadowing, environment mapping, parallax, verticies, alpha channels, billboards, frustrums, etc. with relation to rendering and 3D games.
