If you play Pai Gow Poker, you know the Joker is a Wild Card.

If there is an open seat, one of the extra unused hand is called a Dragon Hand.

The hand is offered to the other players to play the second hand on a rotation and is optional. Usually a player will opt to play the dragon hand if their original hand has a low probability of winning. The dragon hand is not allowed to bet the bonus bet.

IMO, an explanation as good as any I can think of.