Barter trade without money as a medium. It is the original form of commodity exchange. Barter has the following disadvantages: double coincidence of demand; Unlimited extension of trading series; It is difficult to establish a consistent cross-exchange ratio; Lack of universally accepted means of value storage; Double coincidence of time; Geographical restrictions, so barter cannot prevail in today's society.

The essence of modern money is still to meet the demand of "barter", but modern "barter" is no longer a simple exchange of material products, but includes the expanded "barter" of all human labor achievements, and the most typical representative is the tertiary industry-service industry. In addition, the status of mental workers is very special, and it is not appropriate to classify them as the secondary industry or the tertiary industry. On the one hand, many of their labor achievements depend on the workers in the secondary industry to turn them into real material products. On the other hand, their intellectual achievements such as analysis and decision-making have great influence on the production and consumption independent of material products.

On the whole, modern money embodies the following characteristics: first, it represents human labor more truly and comprehensively; Second, the credibility is getting higher and higher. Due to the development of digital technology and financial industry, the amount of real money actually needed in circulation has been greatly reduced; Third, the time span is getting bigger and bigger, and the popularity of forward transactions such as futures and credit cards has brought great flexibility and uncertainty to human social and economic development; Fourth, as a powerful political tool, its position is gradually weakened, replaced by technical output, ideological output and cultural output; Five, the social value formed by historical accumulation and the resulting collection value.

The history of human use of money began from the earliest era of material exchange. In primitive society, people bartered for the materials they needed, such as a sheep for a stone axe. But sometimes limited by the types of materials used in the exchange, we have to find a mutually acceptable item for exchange. This article is the most primitive currency. 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 used as money.