A monetary system is anything that is accepted as a standard of value and measure of wealth in a particular region.

However, the current trend is to use international trade and investment to alter the policy and legislation of individual governments. The best recent example of this policy is the European Union

European Union

The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

's creation of the euro

Euro

The euro is the official currency of the eurozone: 17 of the 27 member states of the European Union. It is also the currency used by the Institutions of the European Union. The eurozone consists of Austria, Belgium, Cyprus, Estonia, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg,...

 as a common currency for many of its individual states. Modern currencies are linked to physical commodities (silver or gold).
A commodity money system is a monetary system such as the gold standard

Gold standard

The gold standard is a monetary system in which the standard economic unit of account is a fixed mass of gold. There are distinct kinds of gold standard...

 in which a commodity

Commodity

In economics, a commodity is the generic term for any marketable item produced to satisfy wants or needs. Economic commodities comprise goods and services....

 such as gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 is made the unit of value and physically used as money, any other money, such as paper notes, being theoretically convertible to it on demand.