A Counter Trap Card is a special type of card in the game of Yu-Gi-Oh!. These cards are unique because they can only be activated in response to other card effects, specifically during the resolution of a spell or trap effect. They are powerful tools for players, allowing them to negate or counteract the actions of their opponents. To activate a Counter Trap Card, players must have it in their hand and meet any specific conditions stated on the card. Unlike regular trap cards, Counter Trap Cards cannot be activated from the field, making timing and strategy crucial for their effective use in gameplay.