A federal budget is a plan for collecting and spending public money. It includes revenue, mandatory spending, discretionary spending, interest on debt, deficits, and borrowing. These terms are not abstract: they shape taxes, benefits, defense, courts, agencies, grants, roads, research, and services.

Federal revenue comes mostly from individual income taxes, payroll taxes, corporate taxes, excise taxes, customs duties, fees, and other receipts. Revenue depends on law, the economy, wages, profits, enforcement, and timing.

Federal spending includes benefits, grants, contracts, salaries, defense, health programs, income support, interest, research, courts, public safety, and agency operations. Some spending is controlled each year; other spending follows formulas in permanent law.

Shutdowns happen when appropriations lapse. Debt-limit fights happen when borrowing authority becomes a deadline. Deficit debates ask whether yearly borrowing is too high. Tradeoff debates ask what the government should do, what it should stop doing, and who should pay.