Poker hole cards are the cards every player should keep a secret from their opponents. Almost every poker variant in the world uses hold cards as part of the gameplay.
The most obvious and common example of this is in the Texas Hold’em variation. Each player participating in the round gets two hole cards. They can combine these hole cards with the available community cards to make the strongest combination.
But, no matter what, they should never show their hold cards to any of their opponents until the showdown.