Black Friday is one the biggest shopping days of the year in the United States – and it has become increasingly popular since the concept spread to Britain around four years ago. The shopping frenzy is a boost for retailers such as Amazon, who are hosting a two-week sales event this year, but it also means chaos in stores and supermarkets on the Black Friday on 25 November.

Here are 10 things you need to know about the day.

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Date

Black Friday always falls on the day after Thanksgiving in the United States. This year, the shopping extravaganza takes place on Friday 25 November, while Cyber Monday is to take place on Monday 28 November.

Many Black Friday deals and sales have already started to appear.

Cyber Monday

The concept was born in 2005 when the National Retail Federation (NRF), an American trade association, noted a surge in online sales on the Monday following Thanksgiving in the US. Christening the day Cyber Monday, the NRF sent out a press release stating the day was one of the biggest online shopping days of the year.

Disaster

Black Friday may now be synonymous with shopping, but that hasn't always been the case. One of the most significant events described as Black Friday was the Fisk-Gould Scandal in 1869 – a financial crisis in the US that occurred when financiers Jay Gould and James Fisk tried to corner the gold market.

Philadelphia

The term Black Friday originated in Philadelphia in the 1950s and 1960s, when police described the traffic congestion that marked the start of the festive shopping season. Attempts to rename the day Big Friday failed. The use of the phrase Black Friday spread after it was referred to in the New York Times in November 1975.

Numbers

Although the day came from the US, it has grown in popularity in the UK. On Black Friday last year, Amazon sold more than 7.4 million items in the UK alone – which is around 86 items sold every second.

Black Friday
Black Friday officially takes place on 25 November in 2016 Oli Scarff/Getty

Violence

Although 2015 was somewhat quieter, Black Friday is renowned for supermarket brawls and violence among shoppers desperate for bargains. In 2011, a woman in a Californian Walmart used pepper spray on other shoppers, reportedly injuring 20 people. The following year, two people were shot during a dispute over a parking space outside a Walmart in Florida on the day.

Stampede

In Long Island in 2008, a Walmart employee was killed in a stampede of shoppers at a Black Friday sale in the store. Other workers were trampled, including a woman who was eight months pregnant.

International

The concept of a shopping day – or shopping weekend – has spread around the world from the US. Since 2011, Mexico has held a shopping event called El Buen Fin – which is linked to the anniversary of the country's 1910 revolution, and occasionally falls on the same day as Thanksgiving.

Workers rights

Retail workers are more susceptible to verbal or physical abuse and/or attacks during the shopping frenzy of Black Friday. Last year, Usdaw, the union of Shop, Distributive and Allied Workers, revealed the number of incidents against retail staff increased by two thirds in 2014.

Buy Nothing Day

Buy Nothing Day, also marked internationally on 25 November, challenges people to take part in a 24-hour moratorium on spending and shopping as a backlash against over-spending and consumerism on Black Friday.