What is Black Friday in the US?

Answer 1

There is more than one kind of Black Friday.

In the US it usually means the Friday directly following Thanksgiving (4th Thursday in November) when many, many retailers offer insane deals and their likewise insane customers descend on the stores in the wee hours of the morning to get said deals.
Most 'black' days are when something bad happens, like a Stock Market crash. This one is a good 'black' day. This is the big shopping day when the stores finally get out of the 'red' (losses were written in red ink in old account books) and get into the 'black' (profits were written in black ink).

In the financial world Black Friday can refer to:
September 24,1869 when the stock market dropped precipitously after speculators tried and failed to corner the gold market. The gold market collapsed and took the stock market down with it.
Or to October 25, 1929, one of several 'black' days leading up to the Great Depression of 1929. The first day of real panic was Black Thursday October 24. More trouble came on Black Friday and Black Monday. On Black Tuesday October 29 the market sank to even more devastating lows.

The reason it's called 'black' is that people wore black when a family member died and draped black cloth on their house door, and everyone wore black to a funeral. So it was like a funeral for the stock market.

The term Black Friday has also been used for all kinds of bad events that happened to happen on a Friday.