The U.S. dollar is the official currency of the United States and is represented by the symbol "$" or the code "USD." It is one of the most widely used currencies in the world, serving as a global reserve currency for many countries. The dollar is issued and regulated by the Federal Reserve, the central bank of the U.S. The U.S. dollar is divided into 100 smaller units called cents. It comes in various denominations, including coins (such as pennies, nickels, dimes, and quarters) and paper bills (such as $1, $5, $10, $20, $50, and $100). The dollar's value can fluctuate based on economic factors, including inflation and interest rates.