Federal workers will go back to work eventually — but it might be a while before they get their paychecks.

The United States federal government shut down at 12:01 am on Saturday as Republicans and Democrats remain in a standoff over the spending bill. But how it the shutdown end? Essentially, Congress has to reach a deal on a spending bill, which it hasn’t been able to do yet.

The government has official shut down 18 times since the modern process that Congress uses to pass budget and spending bills took effect in 1976 — although this is the first time it’s happened under single-party control. The shutdown doesn’t mean all governmental operations cease entirely, but instead “nonessential” activities do. Which means the mail will keep coming, and Social Security checks will go out. But passport processing applications will come to a halt, and most federal employees will be furloughed.

“Congress would have to pass either another continuing resolution or permanent appropriations bill, and then funding is restored and workers are brought back,” Columbia University political science professor Greg Wawro told me. “Assume non-essential workers are furloughed, offices close, communications go out and then, basically, they just reverse the process.”

As Vox’s Tara Golshan and Dylan Scott recently explained, there are multiple avenues for legislative action:

That means Congress can 1) pass the appropriations bills, likely in an omnibus, which just crams together 11 appropriations bills into one spending package; 2) pass a “continuing resolution” (CR), which would fund the government at its current levels, basically buying more time to negotiate the actual appropriations bills (this is what Congress has done since last October); or 3) pass a “CRomnibus,” which is a combination of the two, extending the deadline on certain more contentious appropriations — Read More Here