Commodity money forms the basis for understanding modern monetary systems. Different types of money, like fiat and credit, have evolved from commodity money. Each type of money serves specific functions in capitalist exchanges, leading to their development. The value of each type of money is determined differently: through hoarding, quantity specification, or credit transactions. Commodity money's intrinsic value can influence the value of other forms of money. The quantity theory of money helps explain the value of fiat and credit money in certain situations.