Source: Yugioh Wikia
To Negate a card is to prevent a card from activating and/or using its effect. Destroying a card is not the same as negating the card. Such card examples are:
- Using Seven Tools of the Bandit on Royal Decree
- Using Magic Jammer on Monster Reborn
- Using Trap Jammer on Mirror Force
- Using Skill Drain on Chaos Sorcerer
- Using Solemn Judgment, Horn of Heaven and Forced Back on the Summoning of Jinzo
To negate an attack is to stop a battle from taking place and preventing the monster from attacking again during the same turn. Examples include "Magic Cylinder, "Draining Shield" or "Negate Attack".
Note that cards such as "Sakuretsu Armor", "Mirror Force" and "Dimensional Prison" do not negate attacks. The attacking monster is removed from the field during the Battle Step and the attack ends.