In Omaha each player is dealt four cards rather than the two with Texas Holdem. The players all share the community cards. The community cards are dealt just as they are in Texas Holdem. The first three cards are the flop, the fourth is the turn and the final card is the river. Prior to the flop and after each round there is a period of betting.
In Omaha you must use two of your four cards. An example of this would be if you were dealt Q-2-3-4. The flop is dealt and the cards are A-K-J. The turn is a 10. You do not have a straight. You can only have a straight if you had a Q plus one of the other cards shown in the community cards.
It is more complicated in strategies because everyone has four cards. Think of it in terms of Holdem. In Holdem you get two cards 8h-9d. You have the chance to hit an eight, a nine or a straight. It's pretty straight forward. In Omaha you have 8h-9d-Ah-2s. You have all three options you would in Holdem. You also have flush possibilities, mid straight or low straight, A's or 2's or any combination. If we only look at the denomination of the card only and leave out the suit options we have 8,9 in holdem. In Omaha having 8,9,A,2 you actually have 6 possible hands to look at-89,8A,82,9A,92,A2.
Imagine playing Holdem with six hands to choose from. It sounds like it would be great until you realize everyone else has six hands too. Holdem tends to be a game of pairs because of this. Omaha is a game of flushes and full houses. Most of the time if you don't have the nuts, someone else does.
Because of the nature of the game the best hands tend to be high cards and midrange straight cards. High flushes are often worth chasing also.
One of the biggest mistakes Holdem players make when they move into the Omaha arena is to think they can bluff the same way they did in Holdem. It is much harder to bluff in Omaha mostly due to the fact that with four cards each someone is apt to have the cards you need. If you have a straight and there is a possible flush on the board the chances are high that someone has the flush and you will lose your bet. Don't think for a minute having the flush gives you the win because it only takes pairing the board for someone to snatch the pot from you with a full house.
