Gutshot

You're on the button with 9-8 offsuit. The flop comes Q-10-2 rainbow. Only a jack fills your straight — the board hands you no open-ender, just one rank slotting into the middle. Four jacks are left, so you're an underdog to hit on the turn, about one card in twelve.

That narrowness is the point. A gutshot is the easiest straight draw to hide. On Q-10-2 opponents read open-enders, not a single-card fill, so when the jack lands you get paid off by top pair or a set that never saw it coming. It also works as a semi-bluff: four outs plus a well-timed raise can fold out better hands even on the cards you miss, especially heads-up against someone who checked to you.

The beginner mistake is playing a gutshot like a real draw when the pot doesn't pay for it. Four outs is half of what an open-ender gives you, and calling a big bet to chase one bleeds chips quietly. A pot-sized bet needs about 33% equity to call; a bare gutshot on the turn has closer to 9%. Unless a second draw rides along — an overcard, a backdoor flush — or the implied odds are fat because your opponent is deep and predictable, folding is the play.