At first, in ancient China, people used shells as a media to exchange things. But than, people found that it's hard to tell how much a shell worth, so money had been invented.
Then, different kinds of money started to appear in the market. This brings up the problem that people in different area are not able to trade as they are not using the same type of money. Then, emperor of Qin dynasty decided to unify the money.
There should be a unified form of money!
This is the first time that money is unified and used in a market, and people from different area can trade without any obstacles. Also, for the first time, metal coins was made.
Then, throughout the centuries, the money changed from one form to the other while the dynasty and emperor changed. In Song Dynasty, the first kind of paper money, which is called "Jiao Zi" , was started in used. However, because of the overusing by the government, "Jiao Zi" was band from the market. Then, people started to use metal currency again.
In 1948, the first set of RMB was promoted by the government. This is when the paper money actually got an value, and it started to replace the role of metal currency as it was lighter.
Nowaday, as the technology is much more developed, credit card and online payment is becoming more and more popular in China.