The federal reserve a.k.a the central bank is not federal but private and lends money to the government and national banks.
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These banks then lend to other banks also at interest.
The banks then use the money and depositors money to make loans with interest.
However they use the fractional reserve system where for every dollar shown in the banks books they can lend 1000.
The borrowed money to the government is paid back in taxes but the taxes never cover the debt or cost to run the government.
Hence the national debt at 23 trillion with just 350 million in the population divided by the debt ever growing.
You do the math or look up national debt clock to see it racing paying attention to the owed box.