I found those line which they looks unfamiliar to me. So, please explain what do they mean, and what are there purposes. Thanks.
'hot_weight_a_age' => 'Relative weight of last answer age for hotness:',
'hot_weight_answers' => 'Relative weight of number of answers for hotness',
'hot_weight_q_age' => 'Relative weight of question age for hotness',
'hot_weight_views' => 'Relative weight of number of views for hotness',
'hot_weight_votes' => 'Relative weight of votes for hotness',