The Graveyard is a place to put the cards that are destroyed or otherwise sent there. There are few cards that bring cards out of the Graveyard, so one could refer to the cards in the Grave as "Dead".
The graveyard is a special case within the game as it's considered a zone, such as there's a Removed From Game zone, the library, the "In Play" zone or the "Battlefield" or as in Commander, the Commander Zone. The graveyard is NOT allowed to be changed within order of cards as they're sent to the graveyard as there are a few specific rules pertaining to the graveyard in specific and in major tournaments, if the graveyard is meddled with you are generally disqualified.
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