Look

To look or look at a card is to see the entire card's face.

You can look at any time during the Duel to your opponent's face-up cards, cards you control, cards in your hand, in your Extra Deck, in both yours and your opponent Graveyard and Banished Zone. But not your opponent's face-down cards, cards in their hand, in their Extra Deck, or in both yours and your opponent's Main Deck; unless with a card's text, or just to prevent cheating. For example, when an effect requires your opponent to search for a card of a specific type in their Deck, then they must reveal the card to you; And if they have none left in their Deck, then they must reveal their Deck.

Before you look at your opponent's cards, you must ask for a permission first. The opponent is not allowed to refuse or ignore the request if its not against the rule; they may be penalized for doing so. After looking to the cards, they normally return to their original position. The order of the cards in the Graveyard should not be changed.

Some cards like "Question" can prevent the player from looking to the card in specific zone.