They generate questions like:
where did you go this morning?
When did you woke up this morning.
What did you do after breakfast?
What did you do today at Golden Gate Park.
GPT is all about probabilities. So the LLM know what might be most related answer of a doc chunk.
It works much better than embedding the whole sentence because "When did you woke up this morning" might not be very similar with "Today I woke up at 9.am, had a light breakfast and then went on a run in Golden Gate Park.".