Sacrificing is purposely or forcefully removing a permanent from play. This can be due to an effect on the card itself, the effect of another permanent already in play, coming into or leaving play or a spell such as a instant or sorcery. A sacrificed permanent cannot be regenerated.
From the Comprehensive Rules:
- 701.14. Sacrifice
- 701.14a To sacrifice a permanent, its controller moves it from the battlefield directly to its owner’s graveyard. A player can’t sacrifice something that isn’t a permanent, or something that’s a permanent he or she doesn’t control. Sacrificing a permanent doesn’t destroy it, so regeneration or other effects that replace destruction can’t affect this action.
- 217.4. Graveyard
- 217.4a A graveyard is a 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.
- 502.19. Echo
- 502.19a Echo is a triggered ability. “Echo [cost]” means “At the beginning of your upkeep, if this permanent came under your control since the beginning of your last upkeep, sacrifice it unless you pay [cost].”
- Arms Dealer -
Creature - Goblin 1/1
, Sacrifice a Goblin: Arms Dealer deals 4 damage to target creature.
- Cruel Edict -
Target opponent sacrifices a creature.
 Creatures that prevent/prohibit sacrificing