Stage 1: Barter
In primitive society, people exchanged their own materials for other materials to meet more material needs, such as exchanging a sheep for a stone axe. This is "barter exchange". "Xia" has a clear record of "Japan and China are the market, to the people of the world, to gather the goods of the world, to trade and retreat, and each to get his own place". 
With the continuous enrichment of materials and the continuous increase of people's needs, there are many drawbacks in barter exchange. For example, I have a sheep, and now I need a bag of grain, and the person who has grain does not need a sheep, but a stone axe, and we cannot reach an exchange; another example, I have a sheep, and now another person uses A stone axe in exchange, however I think one of my sheep is worth more than a stone axe, so there will be problems in the exchange as well. 
The purpose of the exchange is seldom accomplished at one time, and it is often accomplished after multiple exchanges.
Stage 2: Barter mediated by general equivalents
Due to the drawbacks of barter, people separate some objects with universal exchange value that are recognized by all people from commodities. As general equivalents, they can exchange for the products they need anytime, anywhere.
In Chinese history, shells, grains and cloth have long been used as general equivalents in commodity exchange. In ancient Persia, Italy, India and other places, cattle and sheep were used as the exchange of general equivalents. 
Common commodities that serve as general equivalents have great limitations, and gradually there are many disadvantages. For example, grains are not easy to store for a long time, and cattle and sheep are inconvenient to carry and divide.
Stage 3: The Generation of Money - Metal Money
The problem exposed by the common commodity as the common equivalent makes people gradually use the metal that is easy to preserve, circulate and divide to replace the common commodity as the common equivalent, and money is produced. Such as Chinese knife coins, copper coins, etc.
Metal currency also has its drawbacks. It is inconvenient to carry in bulk and long-distance transactions, and cannot satisfy the circulation of commodities.
Stage 4: Banknotes
Later, paper money was produced to replace metal currency. The earliest paper money in the world was the "Jiaozi" that appeared in Sichuan in the Song Dynasty of China. Paper money is generally issued by the state or a bank authorized by the government. It is a kind of credit currency. The paper money itself has no value, and the value of the currency is given by the credit of the national government. The vigorous development of trade.
Stage 5: Bookkeeping Currency
With the development of the Internet, we have transitioned from paper money to bookkeeping currency. For example, paying wages is just adding numbers to bank card accounts, and buying clothes is just subtracting. During the whole process, the bank is keeping the books, and only the bank has the right to keep the books. We deposit the banknotes into the bank, the bank sets up a ledger and records it as income on the ledger, and when we transfer money or spend and pay to others, the bank records it on the ledger as an expense for me, and as an income for the other party, the whole process It's just that the data on the ledger changes, without the need for banknotes to participate in the actual exchange process, which is the bookkeeping currency.
On a small island called Yap in the Federated States of Micronesia in the western Pacific, the indigenous people on the island still in the primitive economic stage use a huge stone plate as currency, called Fei. Because the fee is too huge to be used for circulation, after each transaction, the new holder of the fee does not need to remove the fee, nor does it mark the fee, but just let it stay in place, and the accounts will offset each other in the future. (similar to the role of liquidation). Someone even lost a piece of the fee into the sea, but everyone still agrees that he still holds the fee, so he can still buy things. Therefore, Yap's "fee" is not so much a "general equivalent" as it is a bookkeeping system, that is, a bookkeeping currency.
The sixth stage: digital cryptocurrency based on blockchain technology
In the current monetary system, the central agency has the right to issue, control and book the currency. In the past and present, the excessive issuance of currency has caused inflation and caused serious crises. For example: the global financial crisis in 2008; the Greek debt crisis; Zimbabwe's excessive issuance of banknotes caused severe inflation, and the Zimbabwe dollar became a junk currency.
In 2008, a person named "Satoshi Nakamoto" published a paper "Bitcoin: A Peer-to-Peer Electronic Cash System", proposing a new currency system, everyone has the right to keep accounts, the currency cannot be over-issued, the entire The ledger is also completely open and transparent. Combining modern computer technology and cryptography to ensure its security, the first digital cryptocurrency "Bitcoin" was born in 2009, and its underlying technology is called blockchain.
The digital cryptocurrency actually maintains an open and transparent hyperledger through blockchain technology, and solves the problem of trust between people through technical means, rather than relying on central agencies.