Sometimes when a spell or ability resolves more than one player is instructed to perform an action at the same time. When that happens choices of what to do are taken in APNAP order. This means that the active player chooses what he or she will do, then the nonactive player makes his or her choice. Then the actions are performed at one time.

For example, when a Serum Raker goes to a graveyard, its ability triggers. When this trigger resolves all players discard a card. Technically what happens is that the active player chooses a card, followed by the nonactive player choosing a card. Then both of these cards are discarded at the same time. Keep in mind that the active player does not choose and reveal his or her card, he or she just chooses it. In other words the nonactive player will not know what the active player is discarding until after he makes his choice and both cards are discarded.