This week, people around the world will spend millions on clothes, toys, computers and even fridges on the most important shopping day of the year. But why? What is Black Friday all about?

What is Black Friday? It is the popular name for the day after US ThanksgivingThe holiday is traditionally a time to come together with family and give thanks for the year.. When shops reopen after the Thursday holiday, they put on the biggest sales of the year.

Lots of people see Black Friday as the first day of the holiday season. They use it as a chance to buy all their presents cheaply. In popular stores, people even queue outside the door before it opens in the morning.

How did it get its name? For many years, a "Black Friday" was when lots of things went wrong. It was first used to describe the day after Thanksgiving in the 1950s. People would spend it shopping before the weekend. It was unpopular with police in PhiladelphiaThe largest city in Pennsylvania, USA, with a population of one and a half million. because the busy shopping streets meant they had more work to do.

Now, many people believe Black Friday describes the day that shops move out of the "red" and into the "black". This means that they have started to make more money than they need to spend, so they can offer their products at a lower price.

Is it just an American thing? Not any more! The tradition may have begun in the US, but in recent years shops in countries all around the world have started taking part. It is a great way to buy gifts for Christmas at much cheaper prices.

Each year, British people spend the most money outside of the US and Canada. But Germany is not far behind, and the seasonal sales are also popular in South Africa, Saudi Arabia and Australia.

Sounds great, what's the problem? Black Friday is not popular with everyone. Some say that it makes us focus too much on spending money and buying presents. They say we should be giving thanks and spending time with loved ones. They also say that buying more is bad for the environment because it encourages us to throw away more.

Others say that big companies like Amazon make too much money from the sales meaning that small shops lose out.

What is buy nothing day? Buy Nothing Day is a kind of protest called a boycottTo withdraw relations from an organisation as a punishment or protest. The word comes from the surname of a Victorian Irish landlord who was subject to a boycott from poor farmers who demanded rent reduction.. It takes place at the same time as Black Friday. It was set up by a group of people who thought that Thanksgiving and the holiday season should not be based on wanting to "have things".

The first Buy Nothing Day took place in 1992 in Canada. Now, people in more than 65 countries take part. For some people, it is a much more meaningful holiday - a chance to celebrate using less, and throwing less away.

Thanksgiving - The holiday is traditionally a time to come together with family and give thanks for the year.

Philadelphia - The largest city in Pennsylvania, USA, with a population of one and a half million.

Boycott - To withdraw relations from an organisation as a punishment or protest. The word comes from the surname of a Victorian Irish landlord who was subject to a boycott from poor farmers who demanded rent reduction.