A side bet paid on your seven cards; it loses below a straight.
It ignores how you split. On the common table the house edge is 7.77% when you are the only Fortune bettor, about three times the main bet. When another player makes four of a kind or better, a fixed amount is paid to players who have a Fortune bet (the Envy Bonus), and the more players bet it, the lower the cost: 3.13% with six.