This article is from the Magic: The Gathering Rules FAQ, by Patrik Linell (pls@claymore.nu) with numerous contributions by others.
To "counter" a spell is to cause it to go to the graveyard without
it having its effect. "Counter" as a noun, as in "put two +1/+1 counters on
target creature" are physical markers placed on a card. A +1/+1 counter is
put on a creature and gives that creature +1/+1.
 
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