What is the meaning of High-low?

Describing a game in which the high hand and the low hand win.

Designating a blackjack card counting technique in which the lowest cards are worth +1 point and the highest cards −1 point, and the counter places higher bets against higher point totals.

Alternative form of highlow (type of shoe)

A card game where a player has to guess if the next card will be higher or lower than the one shown.

Source: wiktionary.org