As this land enters, you may reveal a Forest or Plains card from your hand. If you don't, this land enters tapped.
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"We've been fighting Shinra on this battlefield for a long time. We've settled in for a long war."
—Fort Condor villager
(08/04/2016)
Lands don't have a subtype just because they can produce mana of the corresponding color. Fortified Village itself is neither a Forest nor a Plains, even though it produces green and white mana, so you can't reveal one to satisfy the ability of another.
(08/04/2016)
If an effect instructs you to put Fortified Village onto the battlefield tapped, it will still enter the battlefield tapped even if you reveal a land card from your hand.
(08/04/2016)
If a Forest or Plains is entering the battlefield from your hand at the same time as Fortified Village, you may reveal the other land to have Fortified Village enter untapped.
(08/04/2016)
You may reveal any land card with either or both of the appropriate subtypes. It doesn't have to be a basic land. For example, you could reveal Prairie Stream from the Battle for Zendikar set to satisfy the ability of Fortified Village.
