How you choose between Fold, Call and 3-bet when facing a raise.
If you fold too often to raises, the raiser profits even with weak hands. So estimate the raiser's range (the hands they could hold) from their seat and type, and continue with hands that do well against it. Answering from the blinds is called defending (defend). Example. In the BB with hand 9♠ 7♦, facing a BTN open to 2.5bb, another 1.5bb plays for a 5.5bb pot, so call wide; against a UTG (first seat to act) open, continue much tighter. Against a nit's early-seat open, 3-bet only KK+ and AK.