Yep. The idea is that businesses that are financially "in the red" (bad) start moving "into the black" (good) between Thanksgiving and Christmas in America. Businesses traditionally offer a lot of discounts on the Friday following the American Thanksgiving Day to kick off the insane Christmas purchasing rush. Over time, though, it has grown out of control, with "Grey Thursday," "Cyber Monday" (online), and even "Black November" sales.
"Black Thursday" sales are typified by American consumerism at it's worst, with some people standing in line outside stores for 12 hours or more in the hopes of getting discounts, sometimes setting up tents on the sidewalks. People are injured every year in the rush when stores open on Black Thursday, and in the last decade there have even been a couple of deaths from people getting stampeded. The absolute worst place to be is Wal-Mart (I believe your equivalent is Tesco).
The reality is that the savings are no better than can be found at sales throughout the year, some stores only stock a handful of the advertised items, and some electronics are "special models" wish missing features that are created specifically for that day.
As an American, I must formally apologize to everyone if the insanity of Black Thursday has crept overseas. Nip it in the bud while you can.
