Natural Bluffs and Unnatural Bluffs

Natural bluffs are hands that are easy and obvious to bluff with because they're weak hands that naturally fall into your betting range, often because they're missed draws you semi-blufffed with on earlier streets. For example, suppose the flop is K❤️ Q❤️ 2♠️, you're in position, and your opponent checks. You bet pot, they call. The turn is 2♦️, they check, you bet pot, and they call. The river is a brick (5♠️). Now you have several missed draws like heart flush draws (e.g. 8❤️ 7❤️ for eight-high) and Jack-Ten open-ended straight draws. These hands were natural semi-bluffs on earlier streets because of their strong draws, but are now weak and unlikely to win. Bluffing with them makes sense - they're "natural" bluffs.

In contrast, consider a board like 9♠️ 2♦️ 2❤️ 5 ♣️ 6♦️ with the same action. There are far fewer weak hands you would have bet flop and turn with that are now weak, since there were no draws. Flopped top pairs or overpairs are still good hands. To find enough bluffs here, you need to get creative about which hands to bluff with. These are unnatural bluffs, sometimes called "savage" bluffs because they require betting three times with a hand that never had much equity.

The strategic relevance is twofold. Against weaker players who mainly find natural bluffs but miss unnatural ones, you should call more in spots with many natural bluffs and fold more when there aren't any. Against thinking players, you should work on finding more unnatural bluffs yourself, as they'll be looking for them too.