When glancing at the Polish presidential elections last Sunday, I saw that the results after the closure of the voting offices (21:00) were tagged as being "late poll" results, with an uncertainty of ~2%.
Then at midnight, a new set of results, called "exit polls", were provided, with an uncertainty of ~1%.
Both seem to come from polls done during the day (and not after 21:00) so I do not understand why they would yield different results.
This is certainly not a matter of logistics: results with information on the person asked (for the representativeness of the sample) can be sent real time to a centralized system, and even if they needed say an hour to gather them, the voters between 20:00 and 21:00 are not likely to introduce such a biais.
How are they different?