The 2,3,11, and 12 Bet is a proposition wager on the craps and “yo” bets. The craps numbers are 2,3, and 12, while the yo or yo-eleven is the 11. Separately, these are called the Horn Bets. While you can make a wager on all four, the different numbers have different payouts. The 2 and 12 have 30:1 payoffs, while the 3 and 11 have 15:1 payoffs.
These 30-to-1 and 15-to-1 winnings are (traditionally) the best payoffs in craps, but their house edge is huge. The house edge on the Horn 2 or Horn 12 is 13.9%, while the house edge on the Horn 3 or Horn 11 is 11.1%. These are some of the infamous sucker bets in craps.