A handy primer courtesy of CGP Grey:
By the way, let me apologize in advance if the world is consumed by flesh-eating zombies sometime next week. That seems to keep happening. After last year's zompocalypse, nations agreed to strict corpse-burning protocols and they should, in theory, ensure that no more undead rise to feast upon the brains of the living. But you know how protocols are. There's what's supposed to happen and then there's the nation that shoveled its zombies into a ditch and drove away. So we'll see. More information soon.