A continuation bet, or C-bet for short, means making another bet on the flop after having already bet or raised before the flop – even if the community cards have not improved your hand at all.
Why do players do this? Quite simply: by betting before the flop, you have already represented strength. A continuation bet allows you to continue telling that same story.
For example, you raise before the flop, signaling a strong hand. The flop arrives – and completely misses your cards. Nevertheless, you bet again. To your opponents, it often looks as though you have hit exactly the cards you were hoping for.
A bluff C-bet works particularly well when the community cards appear unfavorable for your opponents, too. Many players will think: “If they raised before the flop and are betting again now, they probably have something strong.”
A continuation bet is a bit like telling a good story. If you make a convincing impression at the beginning, you should stick to the narrative. Whether your story is actually true often remains unknown until no one is willing to fold anymore.