If you know how to play pot-limit Omaha (or "Omaha high"), you are ☀️ well on your way to learning how to play Omaha hi-lo.
As the name suggests, Omaha hi-lo is a "split-pot" version ☀️ of Omaha poker in which players compete for both the "high" and "low" halves of the pot. Omaha hi-lo is ☀️ usually played with fixed-limit betting and often turns up in "mixed game" formats like H.O.R.S.E. (in which Omaha hi-lo is ☀️ the "O") or the popular 8-game mix.
You will sometimes see the game referred to simply as "Omaha 8" or even ☀️ "O/8" or more elaborately as "Omaha hi-lo 8 or better." The name gets styled differently, too, as "Omaha High-Low," "Omaha ☀️ poker high-low" and so on.
Pot-limit and no-limit versions of Omaha hi-lo are also popular, especially online either as cash games ☀️ or tournaments.