Banish, or Removed From Play, is when a card is not in play anymore. There is no specific zone on a game mat for these cards and they are put on a different stack outside of the game mat. many cards gain effects or have stronger effects when a card is Banished. Some cards like Return from the Different Dimension and Leviair the Sea Dragon allow you to summon cards from the banished zone. Some card effect require you to banish cards from your Hand, Field or Graveyard to activate them like Dark Armed Dragon.