It’s been 17 years since the federal government last faced a partial shutdown because Congress and the president couldn’t agree on a spending bill. A lot has changed in that time, leaving federal employees, citizens and even government decision-makers confused about what a shutdown would mean to them.

Here’s the basics as to what you should know about the shutdown:

1. What causes a shutdown? Under the Constitution, Congress must pass laws to spend money. If Congress can’t agree on a spending bill — or if, in the case of the Clinton-era shutdowns, the president vetoes it — the government does not have the legal authority to spend money.

2. Why can’t Congress agree? The Republican-controlled House has passed a spending bill that maintains  spending levels but does not provide funding to implement the Affordable Care Act, or Obamacare. The Democratic Senate insists that the program be fully funded and that Congress pass what they call a “clean” CR, aka a clean resolution that comes with no policy changes.

3. When would a shutdown begin? When the fiscal year ends at midnight Monday. Most federal workers would report to work Tuesday, but unless they’re deemed “essential,” they would work no more than four hours on shutdown-related activities before being furloughed.

4. When would the shutdown end? Immediately after the president signs a spending bill. As a practical matter, it could be noon the following day before most government offices that were shut down would reopen their doors.

5. How long do shutdowns usually last? Most last no more than three days. Some last less than a day.

6. What’s the difference between a shutdown and a debt crisis? In a shutdown, the government lacks the legal authority to spend money on non-essential services. In a debt crisis, the government is mandated to spend money — but doesn’t have the legal authority to borrow the money to spend it.

7. Will I still get my mail? Yes. The U.S. Postal Service functions as an independent business unit.

8. Would a shutdown put the brakes on implementing the Affordable Care Act, or “Obamacare?” No. The state-run exchanges for the uninsured would open as scheduled Tuesday. “The marketplaces will be open on Tuesday, no matter what, even if there is a government shutdown,” President Obama said Friday.

9. Does that mean I can’t get an FHA mortgage? No. The Federal Housing Administration says it “will endorse new loans under current multi-year appropriation authority in order to support the health and stability of the U.S. mortgage market.”

10. What effect would a shutdown have on the economy? Economists say even a short shutdown — of three or four days — would begin to shave decimal points off economic growth.

Check out the full article from USA Today for some more FAQ’s about the shutdown: http://www.usatoday.com/story/news/politics/2013/09/29/questions-and-answers-about-the-shutdown/2888419/