Final answer:
A straight flush in poker is a rare hand that consists of five consecutive cards of the same suit. It's one of the strongest poker hands and is only beaten by a royal flush and a few other hands, depending on the game.
Step-by-step explanation:
A straight flush in poker is a hand consisting of five consecutive cards of the same suit. For example, if you have a 7, 8, 9, 10, and Jack all in hearts, that's a straight flush. It's one of the strongest hands you can have in poker, only surpassed by a royal flush (Ace-high straight flush) and a few other rare hands depending on the poker variation.
In a standard 52-card deck, which has 13 cards per suit (hearts, diamonds, clubs, and spades), the probability of getting a straight flush in a random five-card hand is very small. This rarity is why the straight flush ranks so highly in poker hand rankings.