There is not much to renew but Omaha Hi poker like Omaha Holdem and Omaha Hi Lo is a version of Texas Holdem where players are dealt four hole cards instead of two. The only difference two of the hole cards can be used in order to make the final hand.
Briefly, one of the poker rules has to do with four hole cards. These make Omaha a nine-card game, whereas having more cards to choose from, poker players will typically be able to finish with stronger hands.
In fact, in practice, players will find that the focus in Omaha Hi tends more towards playing their best Omaha Poker hands than playing against the other players.