Spells are cards that play and then go to your graveyard immediately afterward.

After your mana charge step, you can play as many spells as your mana zone can afford, before you attack. If you can't do everything a spell says, perform as much of the card effect as you can. If you can't perform anything the spell says, then the card simply goes to your graveyard.

Some spells have the Shield Trigger ability. If they are broken while in the shield zone, you can reveal that broken shield card to cast it as a spell for no cost.