Historically, gold has played an important role in the monetary system of the world. When paper money was introduced, gold backed up currencies through an international system called the Gold Standard, under which the value of the currency was linked to a fixed price of gold.
The gold standard broke down all over the world after the first war due to inflationary policies, and despite gold having maintained relatively stable worth and the desire of the economies to return to it afterwards. The expansive monetary policies of the central banks and a lack of consensus among the world's major trading economies make returning to the gold standard not feasible.
The United States remained on the standard until the 70's. This change had an impact on the price of gold around the globe, but not even a decade later the price of gold skyrocketed from $35/ounce to about $850/ounce, showing no signs of going down in the future.
As a matter of fact, gold is a strong currency even when it is not used every day as a direct payment method.
Gold can be bought, stored and converted into cash anywhere with ease. Gold is portable, does not deteriorate over time as it does not corrode, rust or spoil, making it the everlasting currency. It is stable as it has only one grade, its divisible, and universal.
The gold market today plays an important role in the international monetary system because it is unlike other investments. By owning gold people can shelter themselves from times of global economic uncertainty.