Do the wights, like the ones that attacked Mormont at Castle Black, have blue eyes?'wights' are just zombies, mindless and probably smelly. assumedly made by whitewalkers who are the fuck-awesome old guys on dead horses.
imagine them as shiny blue magicians that can turn dead sleepy bodies into scary hungry bodies that just want to eat fat sams and mopey johnsnows.
nobody wants that to happen, especially not our johnsnow, so that is why he is sad.
anyway, it seems that whitewalker magic men need Real Human Babies to turn in to other whitewalkers, perhaps with magic or a really good education system.
so yeah:
dead people get turned into zombies by whitewalkers.
whitewalkers turn babies (maybe only special babies? like harry potter was) into whitewalkers.
whitewalkers are neat.
So, where are the whitewalkers? They were marching South. Mance's army seems to have overtaken them?!