Okay, so due to the abundance of similar questions, I've decided to post a quick primer on some common problems that come up in here. Have a quick read through of this to see if your question is already answered before asking something.
Take note that these are just sample questions designed to illustrate a point. So the answer to the Goblin Grenade question, for example, applies to all similar questions about subtypes (Zombie Infestation isn't a Zombie, etc).
Q: Does shroud/hexproof affect _____?
A: Shroud/Hexproof affects targeting and targeting only. How do you tell if something targets? Read the Oracle text. If it uses the word "target", then it targets. If it doesn't, it doesn't. Simple as that. The only exception is a small handful of keyword abilities that use "target" in their rules text, but isn't specifically stated on the card.
Q: Does a transforming card trigger an enters-the-battlefield ability?
A: No. When a card tranforms, it doesn't leave the battlefield and then come back in a new form. It just changes characteristics.
Q: Do Auras target?
A: Sort of. Auras target when you cast them as spells. Once they're in play, they no longer target whatever they're enchanting - so you can't cast them on a creature with shroud, but if an enchanted creature gains shroud later on, the enchantment won't fall off. Also, if the Aura is coming into play without being cast (through Retether, for example), then it doesn't target.
Q: Does protection affect _____?
A: Protection from FOO means the following (abbreviated DEBT):
Any damage that would be dealt to the protected object by sources with the quality FOO is prevented.
The protected object can't be enchanted or equipped by Auras or Equipment with the quality FOO.
The protected creature can't be blocked by creatures with the quality FOO.
The protected object can't be the target of spells with the quality FOO or abilities from a source with the quality FOO.
If the _____ in question does none of thes ethings, then protection doesn't interact with it (for example, a Black Knight will be destroyed by Wrath of God).
Q: Are Forests green?
A: No. A card's colour is determined by one of three things:
1. The colours of mana in its mana cost.
2. Text that states its colour (Crimson Kobolds, Transguild Courier).
3. For tokens, the effect that craeted them.
Since none of these apply to lands (usually - Dryad Arbor has text that makes it green), lands are colourless (unless an effect gives them a certain colour).
Q: How does Ascendant Evincar interact with a creature that's both black and red?
A: A multicoloured creature counts as all of its colours. If a creature is both black and red, then it's black. If it's black, then it isn't nonblack. The fact that it's also another colour besides black doesn't change the fact that it's black and therefore not nonblack. A black/red creature would get +1/+1 from Ascendant Evincar, would count towards Leechridden Swamp, and can't be targeted by Doom Blade.
Q: Does a card that affects all creatures (like Evacuation) also affect creatures in the graveyard?
A: "Creatures" only exist on the battlefield. In the graveyard, they are "creature cards", which the game sees as a different thing. Since Evacuation refers only to "creatures" and not "creature cards", it only affects creatures on the battlefield. Look at the wording of Soulquake.
Q: Can I block with a creature and then tap it to activate its ability?
A: Yes. A tapped creature can't be declared as a blocker, but there's nothing stopping a creature that's already been declared as a blocker from tapping. Furthermore, tapping a blocker doesn't affects its status as a blocker in any way - it's still blocking, and will still deal and receive combat damage.
Q: If I block a creature with flying with another creature with flying, then my creature loses flying, is it still blocking?
A: Yes. Flying (and other evasion abilities like landwalk, protection, or shadow) only affect how you can declare blockers. Once the blocker has been declared, gaining or losing the ability (or whatever else is relevant to the evasion) doesn't affect its status as a blocker.
Q: Does turning a face-down creature face up, or turning a non-creature permanent into a creature, give it summoning sickness?
A: No. Summoning sickness cares only about how long you've controlled the permanent, not how long it's been a creature for. In addition, it won't trigger any enters-the-battlefield effects.
Q: Is Goblin Grenade a Goblin card?
A: No. A card is a Goblin card only if it has "Goblin" written on its type line.Simply having the word "Goblin" in the name or having an effect based on Goblins doesn't make the card itself a Goblin.
Q: Can I Stifle _____?
A: Activated abilities are written in the form "Cost: Effect". For example, Steel Overseer's ability, planeswalker abilities, and the equip ability are all activated abilities. Triggered abilities begin with the word "at", "when", or "whenever". If the _____ in question doesn't fit into either of those descriptions, then no, you can't Stifle it.
Q: What's a mana ability?
A: A mana ability is one of two things. An activated ability is a mana ability if a. it can produce mana when it resolves; b. it has no targets; and c. it's not a loyalty ability (it doesn't add or remove loyalty counters as a cost). A triggered ability is a mana ability if a. it can produce mana when it resolves; b. it doesn't target; and c. it triggers off another mana ability. For example, Birds of Paradise, Heartbeat of Spring, and Fertile Ground all have mana abilities. Soulbright Flamekin, Koth of the Hammer, and Lotus Cobra don't.
I'll update this with more questions as they come.