USD is the acronym for United States Dollar, which means US dollar, the American currency. The dollar is the country's official currency, but it is also used in several countries around the world, in free circulation, and especially as international reserves.
ISO 4217 establishes the international three-letter code for the various currencies. THE acronym USD refers to the US dollar, written before numeric value, to demonstrate that that amount is in dollars. The International Monetary Fund refers to the dollar with the acronym US$, an abbreviation that is used outside the United States.
The term dollar comes from thaler, which is the abbreviation of Joachimsthaler, an ancient used silver coin that originated what is called the dollar today. The dollar was once one of the most used currencies in the world, but it currently regulates with the euro, in terms of importance. The variation of the dollar fluctuates according to the market, and it can be either low or high.
The United States has both notes and currency, and any amount less than one dollar is issued in currency.
USD is also an extreme sports brand that manufactures skateboards and skates.