i need someone to explain this paper in direct language, because this paper keeps saying things like "internalizes the corpus to retrieve into a LLM via a natural language indexing architecture." but never ever explains what the heck "internalizing" means, and where the "natural language index" sits in the architecture. Figure 2 is the only thing somewhat resembling an arch diagram and just uses these vague undefined terms to describe it. am i missing something or just voicing the same confusion everyone else has?