Magic The Gathering: Repel Intruders?

Question

I don't understand the second effect of this card, it states "Counter up to one target creature " what does this mean?

Answer 1

Countering is a way of stopping something from ever coming into play.  Whenever a spell is played (artifact, creature, instant, etc), it's put onto something called "the Stack."  When this happens, other abilities or spells may be played and put even higher on the Stack.  The way that the Stack works is, the spell highest up on it resolves first.  Here's an example:  Your opponent plays a creature spell.  When he/she does this, that spell is immediately put on the Stack.  Before it can resolve, you play Repel Intruders in response to the spell to counter it.  Your spell would then go on top of the Stack and resolve first if nothing else is played.  If it does resolve, it stops the creature from ever seeing play.  I hope this helps you.  For a better explanation of the Stack and countering, check out the link in my sources.