The national debt of the United States is the total amount of money that the federal government has borrowed over the years to cover the deficit between what it spends and what it collects in taxes and other revenues. It is divided into two main types:

Domestic debt: Treasury bills and bonds issued by the Treasury Department to individuals and American institutions. Foreign debt: Bonds and securities owned by foreign governments and investors.

The debt increases when government spending—such as spending on health, defense, and social security—exceeds its revenues, and it is repaid through refinancing operations and issuing new bonds. Over time, the resulting interest leads to growth in the total amount.