Historical Rules · 1 October 2010
Rule 404.1
Official source text from the 1 October 2010 Rules release
A player's graveyard is his or her discard pile. Any object that's countered, discarded, destroyed, or sacrificed is put on top of its owner's graveyard, as is any instant or sorcery spell that's finished resolving. Each player's graveyard starts out empty.