A counterattack in chess is a response to an opponent’s threat that, rather than defending passively, creates an equal or greater threat in return, forcing the opponent to react.
Instead of retreating, the counterattacking player strikes back. For instance, when facing an attack on the king, a player may choose to ignore the threat and launch a decisive attack on the opponent’s king — if their own threat is faster or stronger, they seize control of the game’s tempo. The key calculation is: "Is my threat more urgent than theirs?"
In practice, counterattacks are most effective in open positions where your pieces are active and coordinated. Before looking for a defensive move, always ask yourself: is there a move that creates a threat strong enough to make your opponent forget about their own? If so, calculate that move first.