The federal budget isn't just one document—it is a year-long negotiation between the President and Congress. This process determines the country's priorities for the coming year.
Every February, the President sends a detailed budget request to Congress. It outlines what the President thinks the government should spend money on and how much revenue they expect to collect.
Congress does not have to follow the President's plan. Instead, they write their own "budget resolution," which sets the overall spending limits for different areas of the government.
Once the limits are set, subcommittees in the House and Senate write "appropriations bills" that provide the actual money to federal agencies. There are usually 12 separate bills that must all be passed to keep the government running.
If Congress can't finish the budget on time (by October 1st), they may pass a "Continuing Resolution" to keep spending at current levels temporarily. If they fail to do this, the government may undergo a "shutdown" where non-essential services are paused.