The website does a bad job explaining what its current state actually is. Here's the GitHub repo's explanation:

Memory Cache is a project that allows you to save a webpage while you're browsing in Firefox as a PDF, and save it to a synchronized folder that can be used in conjunction with privateGPT to augment a local language model.

So it's just a way to get data from browser into privateGPT, which is:

PrivateGPT is a production-ready AI project that allows you to ask questions about your documents using the power of Large Language Models (LLMs), even in scenarios without an Internet connection. The project provides an API offering all the primitives required to build private, context-aware AI applications.

So basically something you can ask questions like "how much butter is needed for that recipe I saw last week?" and "what are the big trends across the news sites I've looked at recently?". But eventually it'll automatically summarize and data mine everything you look at to help you learn/explore.

Neat.