I do not know if Black Friday is equivalent to Friday the 13th. If it refers to Friday the 13th, then it is any 13th day of the month that falls on a Friday. Some people say it is a day filled with bad luck. I personally do not believe it. Any day is a blessing from God.
Black Friday is also the day of shopping after the American thanksgiving day. I heard that during this day, there are many items or products for sale. It is a day where many Americans look forward to. Well, even if you are not an American but you are in America, you could really take part in the said occasion.
Black Friday is also the last Friday before Christmas. I am not aware if this is celebrated.
Good Friday is also called Black Friday by Catholics.