3-Bet in poker refers to a re-raise that can be made both preflop and after the community cards are dealt.
If someone opens the pot by raising and someone makes another raise on top, this is considered a 3-Bet.
For example, let’s assume you are playing a $1/$2 cash game in a 6-max format, and everyone folds to the player in the cutoff position who decides to raise to $6. You are sitting on the button with pocket rockets and decide to re-raise to $20. This move is considered a 3-Bet since you re-raised the original raise made by another player. Learn more about the 3-bet poker strategy.