The government was last partially shuttered on Dec. 22, 2018 as President Trump and Democrats reached an impasse over a spending bill – particularly in regards to funding for border security.

Trump at the time warned the closure could drag on “for a very long time.” The shutdown ended on Jan. 25, 2019.

Prior to the partial shutdown, Trump had urged Senate Republicans to use the so-called “nuclear option” to pass a spending bill that includes enough funding for a border wall. The House scrambled to put together a package late that included the $5.7 billion the president wants but was unable to agree on a deal to fund the government by the deadline.

Senate Majority Leader Mitch McConnell has often rebuffed calls to use the nuclear option, which would change Senate procedure to require only a simple majority to approve the spending bill.

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Fox News asked Marc Goldwein, senior policy director of the Committee for a Responsible Federal Budget – a bipartisan, nonprofit organization that educates the public on fiscal policy issues – to explain a government shutdown, and he answered seven basic questions about the process that Americans should know.

What causes a government shutdown?

A shutdown occurs when Congress and the president fail to sign into law 12 appropriations bills (which determine spending for specific government agencies) in order to continue providing funding for government operations.

How can you prevent a government shutdown?

To avoid a shutdown, members of Congress can give themselves an extension, known as a continuing resolution (CR). The temporary funding measure keeps the federal government open and allows lawmakers more time to negotiate the remaining appropriations bills.

“The bar for a CR is pretty low. You’re not agreeing to anything new politically; it’s a no-brainer,” Goldwein told Fox News.

How long does a government shutdown last?

As long as it takes. Congressional leaders from both parties have to reach an agreement to fund the government.

It usually takes a weekend for this to happen.

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“We’re talking days or weeks – not months,” Goldwein said.

The federal government would be forced to shut down “non-essential services." Who would be affected?

"Essential staff at top level agencies would continue working, but most federal employees whose jobs aren’t vital would likely be sent home," Goldwein said.

For example, those who work at national parks, monuments and museums would be told to go home.

"It doesn’t feel awesome to be told you’re not an essential employee. It's a little demoralizing to go home because you’re not important," Goldwein added.

In the 2013 shutdown, roughly 850,000 employees were furloughed per day, according to the Office of Management and Budget.

But not everyone is required to take unpaid leave.

The president, presidential appointees and members of Congress are exempt. The Postal Service, the TSA and Air Traffic Control will also continue business as usual.

Americans will still be able to get their Social Security and Medicare benefits and food stamps. However, people expecting VA benefits, unemployment benefits, farm subsidies and tax refunds may experience delays.

Do federal employees still get paid?

Most likely. The problem: They're not sure when they'll get their money.

"Everyone loses from the government shutdown. An employee loses their paycheck at the time he or she needs it," Goldwein said. "Ultimately, we’re going to fund it anyway. It’s kind of silly."

Federal employees typically receive back pay shortly upon their return, though, Goldwein says, nothing is certain. Every agency has their own contingency plan in the event of a shutdown.

How many times has the government shut down?

The government has shut down 20 times since 1976, the year Congress introduced the Congressional Budget and Impoundment Control Act, according to the Committee for a Responsible Federal Budget’s research. Half of the shutdowns occurred over a weekend.

“Before 1980, the government didn’t really shut down,” Goldwein explained. “A lot of others were over the course of weekends. I call them ‘fake shutdowns.’”

Goldwein says there have really only been three significant government shutdowns in the history of the U.S.

Two occurred during the Clinton administration in the winter of 1995 to 1996. Former President Bill Clinton and the Republican Congress were at odds and shut the government down for a total of 26 days, Goldwein said.

The third occurred during the Obama administration in 2013 when a stalemate between the House and Senate led to a 16-day hiatus.

How much money can the country lose during a shutdown?

The 16-day government shutdown in 2013 cost the country $24 billion of lost economic activity, according to an analysis from ratings agency Standard & Poor's.

"The payroll cost of furloughed employee salaries alone – that is, the lost productivity of furloughed workers – was $2.0 billion," the Office of Management and Budget reported in 2013.

Goldwein says shutdowns "waste money" more than they "cost money."

"We’re not going to spend more money. We’re just going to spend it on worse stuff," he explained. "Instead of paying employees to work, we’re paying them not to work."

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2018's partial government shutdown cost the U.S. economy $11 billion "due to lost output from federal workers, delayed government spending and reduced demand," according to Forbes.

The Congressional Budget Office further noted the shutdown delayed $18 million in federal spending and led to the suspension of several federal services.

Fox News' Alex Pappas, Judson Berger, Kaitlyn Schallhorn and The Associated Press contributed to this report.