Niambi, Beloved Protector is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Flash When Niambi, Beloved Protector enters, if you cast it, choose target nonlegendary creature card in your graveyard that was put there from the battlefield this turn. Return it to the battlefield. It perpetually gains "Whenever this creature becomes the target of a spell or ability, draw a card. This ability triggers only once each turn."