Buy @ TCGplayer
As Fortified Village enters the battlefield, you may reveal a Forest or Plains card from your hand. If you don't, Fortified Village enters the battlefield tapped.
{T}: Add {G} or {W}.
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.
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.
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.
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.
