The card Mindbreak Trap from Zendikar (Mythic Rare) reads:
2UU
Instant, Trap
If an opponent cast three or more spells this turn, you may pay rather than pay Mindbreak Trap's mana cost.
Exile any number of target spells.
Ok so I understand that spells are only spells while on the stack, so this card does not let you remove everything from the game or of that sort.
So then, what exactly is "Exile any number of target spells."?