First, a government shutdown doesn’t mean the government completely shuts down. Employees and services deemed “essential” would remain in place. About half of the federal employee workforce, however, could be furloughed – sent home without pay.
Government agencies shut down because of the lack of a bill that funds services those agencies provide.
What is a continuing resolution?
A continuing resolution, or "CR," is legislation that funds government operations at the current spending level. In normal years, a bill that funds government operations is signed by Oct. 1, which is the end of the fiscal year. That didn't happen this year.
CRs can fund the government for days, weeks or months. The CR that could be considered Thursday would fund the government through Feb. 16.
Here is a list of services and how they would be affected if a CR is not passed by Friday night:
Air travel would not be affected as federal air traffic controllers would remain on the job and Transportation Security Administration screeners would remain in place.
For about two weeks, federal courts would continue operating normally. After that time, the judiciary would have to furlough employees not considered essential.
The Food and Drug Administration would handle high-risk recalls. Most routine safety inspections would be halted.
Patients in the National Institutes of Health would continue to be treated. New patients would not be accepted until a funding bill is in place.
You could still get a passport and visa applications would still be processed by the State Department. Fees collected when someone applies for a visa or a passport fund those services.
The Federal Housing Administration, the agency that guarantees about 30 percent of all American home mortgages, wouldn't be able to underwrite or approve any new loans during a shutdown, causing a delay for those using one of those loans to purchase a home.
You would still get mail, as the U.S. Postal Service is not funded by taxpayer dollars for everyday operations.
Active-duty military personnel would stay on duty, but their paychecks would be delayed.
All national parks would be closed, as would the Smithsonian museums. Visitors in overnight campgrounds in national parks would be given 48 hours to make alternate arrangements and leave the park.
School lunches, SNAP and WIC
School breakfasts and lunches funded by the federal government would not be affected. The Supplemental Nutrition Program for Women, Infants and Children, or WIC, could be affected. The Supplemental Nutrition Assistance Program, or SNAP, which used to be called the Food Stamp Program, would continue to be funded and SNAP benefits would continue to be distributed. But several smaller feeding programs would not have the money to operate.
The National Weather Service would keep forecasting weather.
Social Security, Medicare and unemployment benefits would be paid, but new applications for those payments could be delayed.
Most services offered through the Department of Veterans Affairs would continue.
Sources: The Associated Press; Politico; the Congressional Research Service