These are the rankings whereupon your hands and the dealer's hands are measured. Whoever has the better ranked high and low hand wins that particular part of the total Pai Gow Poker hand.
Note: Unlike normal poker hand rankings, the ace to five straight/straight flush is considered to be the second best one only beaten by the ace to ten straight/straight flush.
The best possible low hand in Pai Gow Poker is a pair of aces followed by pairs of lesser value.
Often, however, one does not have a low hand pair. Then the highest card counts.
If both you and the dealer hold a low hand ace, the highest valued second card in the low hands will decide the winner. So a low hand of ace, jack beats a low hand of ace, ten and a king, six low hand beats a jack, ten hand.