Continuation bet (c-bet)
A continuation bet, or c-bet, is a bet made by the player who was the aggressor on the previous street, continuing their pressure into a new street such as the flop after a preflop raise.
A continuation bet keeps the betting lead with the player who held it on the previous street. Most often it means the preflop raiser betting the flop after being called, but the same idea applies to a flop bettor firing again as the turn's aggressor. The size and frequency of a good c-bet track range advantage: the more the board favours the aggressor's range over the caller's, the wider and smaller that bet can be, since a small size taxes a weak range cheaply.
Worked example. The pot is 100bb after a raise and a call, and the aggressor c-bets a third of the pot, 33bb:
required fold frequency = 33 / (33 + 100) = 0.248
A bet this small only needs the caller to fold about a quarter of the time to break even as a pure bluff, which is why small, frequent c-bets are so common on boards that favour the raiser.
A c-bet is not automatic. On boards that connect with the caller's range more than the raiser's, checking back and sizing up the bets that do go in usually beats firing on reflex every time.