Money, also sometimes called currency, can be defined as anything that people use to buy goods and services. Money is what many people receive for selling their own things or services.
There are lots of different kinds of money in the world. Most countries have their own kind of money, such as the United States dollar or the Iranian rial.
The idea of bartering things is very old. A long time ago, people did not buy or sell with money. Instead, they traded one thing for another to get what they wanted or needed. One person who owned many cows could trade with another person who had a lot of wheat. Each would trade a little of what he had with the other. This would support the people on his farm. Other things that were easier to carry around than cows also came to be held as valuable. This gave rise to trade items such as jewelry and spices.
When people changed from trading in things like, for example, cows and wheat to using money instead, they needed things that would last a long time. They must still have a known value, and could be carried around. The first country in the world to make metal coins was called Lydia. These first appeared during the 7th century BC, in the western part of what is now Turkey. The Lydian coins were made of a weighed amount of precious metal and were stamped with a picture of a lion. This idea soon spread to Greece, the rest of the Mediterranean, and the rest of the world. Coins were all made to the same size and shape. In some parts of the world, different things have been used as money, like clam shells or blocks of salt.