Poker variants like Omaha and Seven Card Stud exist in two different forms. There is the classical variant in which the player with the highest hand takes the whole pot. Then there is the hi/lo variant, where the player with the best hand (hi hand) splits the pot with the player with the worst hand (lo hand).
There are different definitions for how "lo" a hand has to be. In most online poker platforms, a hand in Omaha or Seven Card Stud hi/lo is lo if it is a combination of 5 cards under 9 with no pairs, though they might make a straight or flush.
The order of cards counts down from 8 and the hands are compared by the highest cards, so that 8, 6, 5, 4, 3 is a better lo hand than 8, 7, 3, 2, Ace.
The best lo hand is a straight from ace to 5:
Splitting the Pot
Usually, the pot is split 50/50 between the best hi hand and worst (that is, best) lo hand. If there are no qualifying lo hands, then the best hi hand gets the whole pot. If two players have equivalent lo hands, then they each get half of the lo share of the pot, or a quarter of the whole pot. The same rule applies for more equivalent low hands, so three lo hands would each get a sixth of the whole pot, and so on.
The same rules apply for players with equivalent hi hands. If a player has both the best hi hand and worst lo hand, he wins the whole pot. This is called a scoop.