California Lowball is a form of poker that's similar to 5 Card Draw, but players vie to make the lowest possible hand rather than the highest. This type of poker is also called A-5 Lowball because aces play low, and straights and flushes aren't considered. Therefore, A-2-3-4-5 is the best possible hand regardless of suits. It's played with a standard 52-card deck, but a single joker is added as a wild card.
After the blinds are posted, the player to the left of the big blind commences the action. After the first round of betting, players have the opportunity to exchange any number of cards for new ones. Then a second round of betting takes place after which there's a showdown, and the lowest hand wins. California Lowball was popular in CA cardrooms during the '70s, which is probably why it got its name.