The total amount of funds borrowed and not yet repaid by the federal government. Federal debt consists of public debt and agency debt.
Public debt is the portion of the federal debt borrowed by the Treasury or the Federal Financing Bank directly from the public or from another federal fund or account. (The Treasury, for example, regularly borrows money from the Social Security trust fund.) Public debt accounts for about 99 percent of the federal debt.
Agency debt refers to the debt incurred by such federal agencies that are authorized by law to borrow funds from the public or from another government fund or account (the Export-Import Bank of the United States, for example).
SOURCE: House Budget Committee