Comparing Hold'em and Omaha is a bit like apples and oranges.
In Omaha the hand equities run much closer together - aces aren't a big favorite against most hands so denying your opponent their equity by making huge over-bets is a good strategy in no-limit. In Hold'em AA is a 4.5 to 1 favorite against smaller pairs - there is no equivalent pre-flop to this in Omaha.
Each player has 4 cards (or 6 hold'em hands at once) and must play two out of their hand and 3 on the board at all times. The hand strengths are very different, in hold'em a pair is a good hand heads-up and two-pair can win multi-way pots and in Omaha you mainly win with straights, flushes and full houses.
Anyways lots of good resources out there if you're interested in playing Omaha.
Good luck to you!