The money value

The money value as the medium of exchange is based on its purchase power. The purchase power shouldn't be based on the inner value. It may be based on the trust of the population that use money.
Bad money (paper) always substitutes the good money (silver, gold). And the second kind is more used as the store of value. The value of money as the store of value is based on its interest rate.
Interest rate is the sum indicated in the percentage equivalent and the sum of credit that the client pays when he/she receives the credit for the use of money for the certain period of time.
The credit is the money or service loan that is given to the debtor on the conditions of returning it with the certain interest. The base of credit is the appearance of permanently free money in the process of money circulation. It plays an important role in the economics.
Money itself doesn't have any value. In fact money is the paper with the certain face that doesn't corresponds to its value. Money substitutes the real money that is depicted in gold. Due to money rules and economics it is impossible to make a lot of money to satisfy needs of all population. The problem is that in such case money will loose its value and won't have any purchase power.
The most valuable money on international level is dollar and pound on local market.