1. The earliest form of money in the world is natural shells. The history of human use of money began in the era of barter, which was caused by the limited types of materials exchanged.

2. Livestock, salt, rare shells, rare bird feathers, precious stones, placer gold, stones and other items that are not easy to obtain in large quantities are regarded as money;

3. Metal currency, after years of natural elimination, the commodities used in currency are gradually replaced by metals. The advantage of using metal money is that it needs manpower to make it, and it cannot be obtained in large quantities from nature. At the same time, rare gold, silver and copper, which are easy to store and difficult to smelt, have gradually become the main currency metals;

4. The production of copper coins is very rough, the design is simple, the shape is not fixed, and there is no use unit. Because the shape is very similar to the shell coin as currency, most people call it a copper shell;

5. Gold and silver, the main coins in the West are gold coins and silver coins, and the auxiliary coins are copper and copper alloys;

6. Paper money, the earliest paper money in the Song Dynasty in China and Sichuan.