In the old age,few centuries ago people uses some money system which is called Barter system to buy and sell their products.This system works like exchanging their products between two people when they are in need but they realized that that system has flaws and not suitable for everyone since if there is no demand for one's product he can't buy anything he needs so later they moved to currencies (paper money) until now people uses this as their main form of payment but in digital format but people needs to understand that this also has flaw of centralization so we need to move to the decentralized money for better life.Lets get update ourselves to use the crypto currencies.
The transition from the barter system to fiat money took longer than that, after the barter system we had commodity currencies, and as the name implies those currencies were made of commodities, people used iron, tea, gold and silver among many other commodities, but gold and silver because of their durability and the great value they have began to be preferred as a form of commodity currencies and then when coinage was created the first form of money was created.
And then someone had the great idea to modify a system that worked perfectly and create pieces of paper that had no value and that the government could print as they wished and fiat was born and as we know that is a terrible way to try to transfer value because the government always abuses their position of power.