"Black Friday" is the Friday after thanksgiving.
http://en.wikipedia.org/wiki/Black_Friday_(shopping)
Traditional day for Apple giving a discount (which they rarely, if ever, do).
Apple have been doing this in the US for ages.
I think this year it is synced globally.
You can buy online (with free shipping), or go in to a retail store, but today only. Only downside for a retail store is they may not have what you want in stock.