The check-raise is checking so the opponent bets and then raising over the top. It's one of the most powerful weapons when you play (you act first), because it turns your positional disadvantage into pressure.
Check-raise for value
You check with a strong hand (a set, two pair, a made flush), let the opponent fire their c-bet, and raise to build a big pot. It works especially well on boards that hit their betting range.
Check-raise as a bluff (semibluff)
You can also check-raise with strong draws (flush + straight). You don't need to have the best hand now: either the opponent folds and you win the pot, or you complete your draw and win big. That's called a semibluff.
EjemploYou defend the blind with 9♥8♥, flop 7♥6♣2♠. You have an open-ended straight draw + hearts. You check, the opponent bets, and you raise: you have tons of cards that make you the winner, and sometimes they fold right there.
⚠️ Error común: Don't check-raise only with premium hands: you become transparent. Mix it with semibluffs to be unpredictable.
💡 Clave: The check-raise balances value (made hands) and semibluffs (strong draws). It's how you take back the initiative without position.