Black Friday is the day following Thanksgiving Day in the United States (the fourth Thursday of November). Since the early 2000s, it has been regarded as the beginning of the Christmas shopping season in the US, and most major retailers (shops) open very early and offer promotional sales. Black Friday is not an official holiday, but California and some other states observe "The Day After Thanksgiving" as a holiday for state government employees.

The term “Black Friday” was coined in the 1960s to mark the kickoff to the Christmas shopping season. “Black” refers to stores moving from the “red” to the “black,” back when accounting records were kept by hand, and red ink indicated a loss, and black a profit. Ever since the start of the modern Macy's Thanksgiving Day Parade in 1924, the Friday after Thanksgiving has been known as the unofficial start to a bustling holiday shopping season.

(wikipedia)