It's basically a LLMs with access to a search engine and the ability to query a vector db.
The top n results from each search query (initialized by the LLM) will be scraped, split into little chunks and saved to the vector db. The LLM can then query this vector db to get the relevant chunks. This obviously isn't as comprehensive as having a 128k context LLM just summarize everything, but at least on local hardware it's a lot faster and way more resource friendly. The demo on GitHub runs on a normal consumer GPU (amd rx 6700xt) with 12gb vRAM.