The debt ceiling is the maximum amount of money the United States government is authorized to borrow to meet its existing legal obligations, including Social Security and Medicare benefits, military salaries, interest on the national debt, and other payments.
A debt limit or credit limit is a statutory limit on the amount of debt that may be accrued by U.S. federal agencies (and thus its citizens). It does not represent any kind of political limitation or constraint on federal spending; rather it reflects statutory limits set forth in legislation passed by Congress that specify how much money may be spent annually by each agency as well as what percentage must be spent each year before additional funds are allocated from elsewhere in order for them not exceed their respective caps set forth under such legislation (such as appropriations bills).
Debt doesn’t mean that you owe money; instead, it simply means that somebody else has agreed to lend money to your government at some point in the future (or right now).