Omaha is similar to Hold’em, except each player is dealt four downcards instead of two. In order to make a hand, a player must use precisely two hole cards with any combination of exactly three boardcards. The betting is the same as in Hold’em.
Omaha is often played high-low split, 8-or-better. You may use any combination of two hole cards and three boardcards for your high hand and another (or the same) combination of two hole cards and three boardcards for your low hand.