how does a currency lose or gain value
Currency appreciation and depreciation In a floating exchange rate system, a currency's value goes up (or down) if the demand for it goes up more (or less) than the supply does. In the short run this can happen unpredictably for a variety of reasons, having to do with trade flows, speculation, or other factors in the international capital market. For example, a surge in purchases of foreign goods by home country residents will cause a surge in demand for foreign currency with which to pay for those goods, causing a depreciation of the home currency.
Gold standard This was meant to be a temporary measure, with the gold price of the dollar and the official rate of exchanges remaining constant. Revaluing currencies was the main purpose of this plan. No official revaluation or redemption occurred. The dollar subsequently floated. In December 1971, the "Smithsonian Agreement" was reached. In this agreement, the dollar was devalued from $35 per troy ounce of gold to $38. Other countries' currencies appreciated. However, gold convertibility did not resume. In October 1973, the price was raised to $42.22. Once again, the devaluation was insufficient. Within two weeks of the second devaluation the dollar was left to float. The $42.22 par value was made official in September 1973, long after it had been abandoned in practice. In October 1976, the government officially changed the definition of the dollar; references to gold were removed from statutes. From this point, the international monetary system was made of pure fiat money.