Debt is an investment with risk (deadbeat default) and reward (interest). People around the world want to buy US government debt because it is regarded as risk free (looking at you, Mr. Trump) and as a result, the interest paid is very low.
In this situation, the government can sensibly chose to finance its operations by borrowing (US bonds) rather than taxing letting foreign investors etc. pay the costs of running the government and letting the money that would have been raised in taxes in the domestic economy where it may more successfully promote jobs and growth.
This basic debt setup baffles talk radio conservatives because it is a strategy that doesn't work for the family budget. Why? Because credit card interest is much higher than Treasury bond interest. Interest payments on the government debt are currently runnning at 1.3% of GDP. Consumers can't match that and conservatives can't understand it.