Full explanation — Backdoor Draw
A backdoor draw, also called a runner-runner draw, requires two subsequent cards on both the turn and river to complete a hand. For instance, if you have two spades and the flop contains one, you need two more spades on consecutive streets to hit a backdoor flush. While the probability of hitting is relatively low, around 4.2% for a backdoor flush, these draws add valuable equity to a hand. This often allows for more aggressive play, turning a marginal hand into a profitable semi-bluff, particularly when coupled with other equity or position.