Cards listed in the "sideboard" are just ones I initially considered for the deck, but weeded out. If you can't get Wrath of God, Day of Judgment works just as well against any except regenerating creatures.
The deck is very cheap, heavy with 1-2-3 casting cost spells. All creatures in the deck are disposable, since they will fall in your inevitable WoG type spells, and because they are so easy for you to get back from the graveyard.
The next big block of spells come at 4, Wrath of God, Cataclysm, Breath of Life, Resurrection. 4 is a magic number, because at that point, you can start mass annihilation (timing is everything).
At 5, you get a few Angels and Defy Death: more dangerous flying threat, and a better system of resurrecting angels.
At 6, you get an Angel, a Giant and a Dragon, all three potential game changers. The Angel of Fury and Alabaster Dragon have identical abilities, one is a 3/5 flyer the other a 4/4 flyer, when either dies, you can shuffle it back into your library. The only way to get rid of them is exiling them; the Sun Titan lets you slowly retrieve those white weenies sitting in your graveyard.
At 7 mana, the game changes: Angel of Glory's Rise will return all your human peons to play from the grave; Debtor's Knell lets you retrieve ANY creature, from ANY graveyard and put it in play under your control (I recommend using this in multi-player)...digging up a dragon or vampire or demon or whatever big nasty thing your WoG wiped out is awesome; Mass Calcify can be a game-ender, simply put, after you have already cleared the board once or twice, everyone is built back up, Mass Calcify wipes out your opponents and leaves you untouched (as long as you aren't facing a white opponent). I generally keep Mass Calcify on my sideboard until I know it'll be useful (no white opponents, and if I run short of mass destruction). Debtor's Knell is probably less useful in head-to-head, unless you know your opponent has a nice selection of creatures you can abuse.
The deck is simple, utilize white mass destruction to obliterate all foes (works especially good in multi-player games) while taking little hurt yourself. Several creatures bounce back to the library, and most of the creatures are low costing creatures with "comes into play" effects, which can be abused by resurrecting them via spell or ability.