The quiz panellists rotate, apart from Alan Davies, who is a permanent panellist, and you can usually find well known British comedians taking part in it, although panellists from all sort of fields have come up to the show.
Faced up with obscure and different questions whose correct answers are bound not to be provided, panellists are compensanted with points for giving interesting answers, whether they are correct or not. On the other hand, if the panellist's answer is not only wrong but also regarded as pathetic, then points are deducted.
Watch a glimpse of one of QI Quiz episodes and guess if you could have been a panellist yourself.
I'm sure que question is going to sound familiar.
You can read all about this TV show on QI: Dave.