At the start of the game, everyone is dealt a card.
You can see your own cards.
You cannot see other players' cards until you either fold or the game ends.
Choose between high or low.
Among those who chose "high", the player with the highest card wins.
Among those who chose "low", the player with the lowest card wins.
Even if another player has the highest/lowest card, they won't be included unless they actually declare high/low. Therefore, declaring high/low becomes the key to winning.
Of course, if you are the only one who declares high/low, you win by default.