Black Friday is an informal name for the day following Thanksgiving Day in the United States (the fourth Thursday of November), which has been regarded as the beginning of the country's Christmas shopping season since 1952.
The earliest evidence of the phrase "Black Friday" used in a shopping context suggests that the term originated in Philadelphia, where it was used to describe the heavy and disruptive pedestrian and vehicle traffic that would occur on the day after Thanksgiving. This usage dates to at least 1961. As the phrase became more widespread, a popular explanation became that this day represented the point in the year when retailers begin to turn a profit, thus going from being "in the red" to being "in the black".
Cyber Monday followed suit, making its debut on November 28, 2005. The term "Cyber Monday" was created by marketing companies to persuade people to shop online.