The royal flush stands as the rarest of hands in poker. In any game that uses standard poker hand rankings, the royal flush beats out all other hands. A royal flush is made when you have a ten-to-ace straight (aka a broadway straight) with all five cards the same suit.
Omaha is a variant of Texas Hold'em Poker. Omaha is considered, by some, to be the hardest game of Poker to master. Of all of the different games of Poker, Omaha is for many the hardest to learn to play and the hardest to bluff in. It is played most often at fixed limits, like Texas Hold'em and pot limit.