Maelstrom Archangel Avatar 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

At end of combat, for each creature you controlled at the time it dealt combat damage to a player this turn, copy a random card with the same mana cost as that creature. You may pay . If you do, choose one of those copies. If a copy of a permanent card is chosen, you may create a token that's a copy of that card. If a copy of an instant or sorcery card is chosen, you may cast the copy without paying its mana cost.