Discussion Forum

a spell is any card as it's being played (except land)

Yes, cancel can counter any spell being cast, including spells received from cascade. Although, i do not know if you can counter a border post being played with its special ability.

http://magiccards.info/scans/en/arb/5.jpghttp://magiccards.info/scans/en/10e/71.jpg

To understand cancel and it's older brother counterspell you need to understand the stack.

Imagine that every card that's played that doesn't say "Is not a spell" on it (everything except 'Land' spells as far as I know) is placed in a pile on the center of the table you're playing on and then when everybody is done they start taking things from the top of the pile and putting them where they belong.

"No" spells are (almost always) instants which go on top of the stack and remove whatever they land on, because as instants you can instantly at any time cast them and stick them on the stack.

What this means is that when something is countered from off the stack it never even existed on the field to begin with. It's like beaming somebody to a planet in star trek but they get killed somehow before they materialize on the surface.

Ok, shadowex has it right, but here's a few things to clarify for visual learners (like me);
say the stack looks like this:
You play Lightning Bolt, it goes on the stack like so.
Lightning Bolt
Your opponent plays cancel targeting lightning bolt, the stack looks like this:
Cancel
Lightning Bolt
Cancel resolves countering Lightning Bolt. Lightning Bolt is taken off the stack and put in the graveyard. The stack is now empty.
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Spells are only spells while they're on the stack, and Lands are not only not spells, but they can't be responded to. Any triggered abilities on the lands however (like Teetering Peaks) can be responded to after the triggered ability goes on the stack. Seems complicated, but once you get used to it you're fine.

Also, on the borderpost line, playing it for its alternate casting cost still puts it on the stack (its alternate casting cost being pay :mana1: and bounce a basic land you control. It can be countered.