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.
A leading bet made postflop and from out of position, usually small, that usually comes from the non-aggressor in the hand. E.g., in no-limit hold'em a player on the button raises and the big blind calls to create a pot of 1,500, then after the flop the big blind leads for 300.