Here we are, once again: Federal spending is set to expire on March 23, leaving Congress a week to negotiate and pass a bill to keep the government open for business.

As of Thursday, Republicans and Democrats had yet to agree on what is expected to be a massive $1.3 trillion piece of legislation, leaving Americans with more questions than answers about what Congress plans to do to avoid a third government shutdown this year. Here are a few:

Q: Why are we doing this again? Didn’t Congress just pass a massive budget deal?

A: Your memory is not failing you. On Feb. 9, President Trump signed the Bipartisan Budget Act of 2018, which increased federal spending by roughly $300 billion over the next two years and ended a brief shutdown. But in Congress, there is a distinction between budgeting and appropriating — that is, setting top-line levels of overall spending and actually directing the money to specific agencies and programs are two different matters. So as part of the budget deal, Congress gave itself another six weeks to work out microscopic details of spending taxpayer money and write an “omnibus” appropriations bill, which packages smaller regular appropriation bills into one larger bill, funding the whole of the federal government.

Q: What are the major outstanding issues?

A: There are a lot of differences between Republicans and Democrats at this point, though they should be resolved in the coming days. The crucial flash points are border security, immigration policy and abortion rights, with a few other issues at play — including health care and one major infrastructure project.

To move the bill through the House and Senate before the government shuts down at 12:01 a.m. next Saturday, a deal will have to be reached and a bill released by early next week. Otherwise Congress could be forced to pass another short-term extension of current funding levels.

Q: What does immigration have to do with federal spending?

A: Even though it’s only March, the omnibus is likely to be the last must-pass bill Congress takes up before the November midterm elections, so lawmakers are exploring attaching all sorts of pet priorities to it. Even though attempts to address the cancellation of the Deferred Action for Childhood Arrivals (DACA) program and Trump’s demands for a border wall have so far fizzled, the issue continues to be litigated as part of the spending negotiations. The Trump administration has floated attaching a short-term DACA extension for young immigrants paired with border wall funding, but there seems to be little enthusiasm for the deal on Capitol Hill — especially since Trump’s DACA cancellation is tied up in court.

But other immigration-related issues are at play: Liberal Democrats do not want any additional money for immigration enforcement included in the spending bill, while conservative Republicans are pushing for language that would allow the Trump administration to pull federal money from “sanctuary cities” that do not cooperate with federal immigration authorities.

Q: What about health care? And why is abortion at issue?

A: Congressional leaders are exploring whether to attach funding that would help health insurers lower premiums on the plans they sell on the exchanges set up under the Affordable Care Act. Those payments have been controversial among conservatives, who consider them unfair subsidies used to prop up former president Barack Obama’s health care law. But with Republicans unable to pass an alternative of their own, there is growing desire in the GOP to move forward with the payments.

There is a catch: Republicans want expansive restrictions to ensure the money is not used to subsidize plans that offer abortions, and Democrats are balking at their proposed language, arguing that it goes beyond an abortion compromise struck when the ACA was passed.

There are other disputes rooted in abortion politics, as well: House Republicans are pushing for language that would allow the Trump administration to direct federal family planning and teen pregnancy prevention grants to groups that promote sexual abstinence. Democrats are opposed to that provision, as well as policy “riders” that would block funding for health-care providers that perform abortions, allow health-care providers to opt not to perform procedures they find morally objectionable and bar funding for scientific research using fetal tissue.

Q: What else could cause problems?

A: A very expensive tunnel under the Hudson River. Key congressional leaders — especially House Appropriations Committee Chairman Rodney Frelinghuysen (R-N.J.) — are pushing to have the bill direct $900 million to the Gateway Program meant to improve rail travel between New Jersey and Manhattan. But the funding appears to have a fierce opponent in Trump, who sees the project as a Democratic priority — particularly for political rival Charles E. Schumer (D-N.Y.), the Senate minority leader — and is in no mood to rubber-stamp it.

Trump has told House Speaker Paul D. Ryan (R-Wis.) that he would veto the omnibus if the Gateway funding is included, and Ryan told a group of GOP lawmakers from New Jersey and New York on Wednesday that the president’s opposition could derail the spending bill.

One key Republican advocate of the project, Rep. Peter T. King (R-N.Y.), buttonholed Trump on Thursday at a St. Patrick’s Day luncheon on Capitol Hill, and argued on behalf of the project. He would not tell reporters afterward whether his lobbying had succeeded in preserving the funding. “It was a very friendly conversation,” King said. “He heard how important it is, and that’s as far as I can go.”

Q: What other goodies might get thrown into the bill?

A: A number of tax provisions could find their way into the bill, including fixes to the Republican tax overhaul that passed in December. One closely watched fix involves a drafting error that has left some agricultural businesses eligible for a key tax break while others are exempt. A bipartisan group of lawmakers led by Rep. Kristi L. Noem (R-S.D.) is pushing to attach legislation that would require online retailers to collect sales tax based on the location of their customers, but there is fierce opposition in some corners. Meanwhile, a handful of lawmakers are pushing for a provision that would allow the Export-Import Bank of the United States, which has been hamstrung by political fights that have left it without a functioning board, to return to full operations, but congressional leaders appear unlikely to add the measure.