A qualifier is the minimum hand strength needed to take part in a payout. In split-pot poker games such as Omaha Hi/Lo and Stud Hi/Lo, half the pot goes to the best low hand, but only if it qualifies, usually by holding five unpaired cards ranked eight or lower, the rule known as eight or better. If no player has a qualifying low, the high hand takes the whole pot.
House-banked poker games apply the idea to the dealer instead. In Three Card Poker the dealer needs queen-high or better, and in Caribbean Stud ace-king or better; when the dealer fails to qualify, the ante is paid at even money and the play or call bet is returned. For operators, qualifier rules shape both the house edge and the player experience, so they must be stated clearly in the game rules.