Your graveyard is still a graveyard. I know the card says that, but it really bears repeating. Cards that would go to your graveyard still will, even while your graveyard is a creature on the battlefield.

While you'll use the cards in your graveyard to determine the stats and abilities of your graveyard-that's-a-creature, those cards aren't themselves on the battlefield. For example, if you mill a card while your graveyard is animated, the milled card doesn't enter the battlefield. This isn't quite as wild as Yet Another Aether Vortex.

Once enchanted, your graveyard behaves like any other creature. It can attack or block. You can enchant it with other Auras, equip it, use it to crew Vehicles, and so on. It won't naturally have any creature types—the text box doesn't include the type line.

Your graveyard-creature will have all the text boxes of all creature cards in it. This means it will have all rules text, flavor text, and watermarks of those creature cards. If a creature card is put into your graveyard, the graveyard-creature will gain its text box. If a creature card leaves your graveyard, that text box will be lost. Phoebe can steal any of these text boxes, but she must do so one at a time.

If a creature card in your graveyard is a double-faced card, your graveyard-creature only gains the text box on its front face. Your graveyard-creature is not a double-faced card and can't transform, no matter how many double-faced cards are in it. Similarly, if a creature card in your graveyard has an Adventure, your graveyard-creature only gains the text box of the creature card, not the Adventure card.

If there's a creature card in your graveyard with an ability that defines its power and toughness, such as Tarmogoyf (Maro: He means Maro), the ability of Animate Graveyard will apply after that ability. The base power and toughness of your graveyard-creature will still be equal to the number of cards in your graveyard.

If the enchanted graveyard would leave the battlefield for any reason, instead Animate Graveyard is exiled. This will cause the graveyard to give up its dreams of being a creature and return to being only a graveyard. The graveyard doesn't die. It just goes back to being a graveyard. No abilities that trigger whenever a creature dies will trigger.

Similarly, if Animate Graveyard leaves the battlefield or becomes unattached from your graveyard, the animated graveyard will return to being just your graveyard.

If another player gains control of your graveyard, Animate Graveyard will be put its owner's graveyard. This immediately causes your graveyard to stop being a creature and return to just being your graveyard.

You can't animate your junkyard or your scrapyard. Though they may aspire to be graveyards, they are not.