The debt ceiling is a legal limit set by the US government on the amount of debt that it can incur. The debt ceiling is set by Congress and is designed to limit the amount of debt the government can take on, similar to how a credit card has a limit to how much someone can spend. The debt ceiling is periodically increased by Congress in order to accommodate the government's need to borrow more money.

Every time the government spends money, it does so by issuing Treasury bonds, which are essentially loans that the government takes out from investors. When the government reaches the debt ceiling, it can no longer issue new Treasury bonds unless the debt ceiling is increased. If the debt ceiling is not increased, the government would need to stop spending money or risk defaulting on its debt obligations.

The debt ceiling has been a controversial issue in recent years, as some politicians argue that it is necessary to limit the government's borrowing in order to control the national debt. Others argue that the debt ceiling is a political tool that is used to create drama and gridlock in Congress, making it more difficult for the government to function effectively.

Regardless of one's political views on the debt ceiling, it is a key aspect of the US government's financial management and has important implications for the economy and financial markets.