WASHINGTON — The Senate is considering sweeping changes to health care this week, but the process itself can be confusing to follow and no one is quite sure what, if anything, it will produce in the end.

To outside observers, this week can feel like the "I’m Just a Bill" song from Schoolhouse Rock remixed with atonal melodies, changing beats, and lyrics in a foreign language.

We’re here to help: This is what you need to know about what’s happened so far, what’s coming up next, and how Congress might actually send a health care bill to the president’s desk.

What have they passed so far?

Let’s time-travel a couple of months back: Our story begins on May 4, when the House passed the American Health Care Act, a sweeping bill to repeal and replace Obamacare.

The House took up the bill using the budget reconciliation process, which allows the Senate to pass legislation with a bare majority, meaning they can avoid a Democratic filibuster. The tradeoff is that there are rules to reconciliation that can limit what they can pass and when they can pass it — more on that later. The Senate is now considering the House bill under those rules.

What were the big Senate votes?

The Senate has struggled to come up with its own bill. But senators on Tuesday took the first step they needed to pass any legislation, when they successfully voted on a motion to proceed to a debate on the House bill.

It’s important to remember this was not a vote in support of any specific policy. But if the vote failed, it would have likely been fatal to Republican efforts to repeal and replace Obamacare, so it was still major news.

Republican Senator from Texas Ted Cruz, center, gets in an elevator after leaving the Senate chamber on Capitol Hill in Washington on June 22, 2017. Michael Reynolds / EPA

The Senate did vote on something more substantive on Tuesday evening: A new edition of the Better Care Reconciliation Act, the replacement bill favored by Senate GOP leaders. The latest version incorporated an amendment by Sen. Ted Cruz, R-Texas, allowing insurers to sell unregulated plans and one by Sen. Rob Portman, R-Ohio, that would add $100 billion to help lower costs for customers. The vote failed 43-57, with nine Republicans voting "no."

Technically, they didn’t vote on the bill — it was a motion over whether to waive procedural rules related to it — but it was widely considered a proxy vote for the legislation itself. An exception in this regard was Sen. John McCain, R-Ariz., who voted "yes" on the motion but clarified through a spokesman the next day that he still opposes the underlying bill.

On Wednesday, there were two more significant votes. One was on the Obamacare Repeal Reconciliation Act, which would repeal Obamacare’s taxes and, after a two-year delay, its Medicaid expansion and subsidies to buy insurance.

A similar bill passed in 2015 only to be vetoed by President Barack Obama, but the new version failed 55-45 with seven Republicans joining Democrats in voting it down. The Congressional Budget Office found it would insure 32 million fewer people than Obamacare after a decade and cause insurers to raise premiums and pull out of markets.

In another vote, the Senate decided on party lines, 52-48, to block a Democratic motion that would order legislators to return the bill to committee with instructions not to include any Medicaid cuts. Spending reductions to Medicaid are a major piece of the House bill and various Senate replacement proposals.

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Things are subject to change as Senate leaders in both parties work out a schedule. But one thing you can count on is more debate: There’s supposed to be 20 hours before a final vote. Republicans can speed things up a bit by yielding their time.

What's a 'Vote-a-Rama'?

When the debate is done, the Senate moves on to what is unofficially called the "Vote-a-Rama," possibly as early as Thursday. During this period, senators from both parties can offer an unlimited number of amendments which are voted on without debate.

This would be a chance for individual Republicans to present their own Obamacare replacement bills, which are unlikely to pass, as well as smaller policy proposals. For example, Sen. Lindsey Graham, R-S.C., has been pushing an amendment to block-grant health care funding to states.

Democrats could use this period to offer amendments that might provide fodder for future political attacks, like measures that would undo unpopular cuts.

Sen. Jeff Merkley, D-Ore., has already submitted over 100 amendments, many of which would require that any bill not affect specific groups like Iraq veterans, pregnant women, and patients battling numerous individually listed forms of cancer.

But there are limits: Their amendments have to be relevant to the bill and they can’t increase the deficit. They also can’t use the process to filibuster a bill by speaking indefinitely.

"There will be some agreement at the end," Sarah Binder, a professor at George Washington University, told NBC News. "This isn’t like Jimmy Stewart in 'Mr. Smith Goes To Washington.'"

On Wednesday night, Democrats added a new wrinkle to the process. Senate Minority Leader Chuck Schumer announced his party members would withhold their amendments in protest until Republican leaders made clear what bill they were actually voting on in the end.

What's the end game?

As of Wednesday night, Republicans had not announced what final legislation they planned to vote on.

The most prominent idea being floated right now is a "skinny repeal" bill that would eliminate Obamacare’s requirements that individuals buy insurance and employers provide it, along with the law’s medical-device tax.

The bill would be compiled through amendments in the "Vote-a-Rama," possibly in a substitute amendment at the end that's backed by Senate leaders.

If the House passes the same skinny repeal bill as the Senate, it goes to the president’s desk, and it becomes law.

This could cause serious disruption in insurance markets and some Republicans sound wary about the idea.

Democrats presented their own guess at what a "skinny repeal" bill might look like to the CBO on Wednesday and the agency found it would lead to at least 16 million more people going uninsured. A senior Democratic aide told reporters the CBO also found it would raise premiums by 20 percent, which would be in line with prior estimates of the effects of undoing the individual mandate.

Another possibility is that the House and Senate decide to go to conference to work out their differences on a broader replacement bill. Some Senators are already saying they might vote for a skinny repeal bill with this outcome in mind. Once the conference committee agreed on a bill, it would go to both the House and Senate for a vote with no further amendments.

Finally, the House and Senate could also work out a final bill without going to a formal conference committee.

What could go wrong?

Remember those special rules that Senators need to follow to pass a bill using reconciliation? This is where they become a big deal.

Under reconciliation, anything in a bill has to directly affect the budget. This is known as the Byrd Rule and certain provisions in the House and Senate replacement proposals so far may not pass muster.

The Senate parliamentarian is tasked with weighing these issues and, according to Democrats on the Senate Budget Committee, has already issued guidance that various key provisions in the Republican bill are likely to violate the Byrd Rule and thus require 60 votes to pass.

Among other items, the current guidance would rule out language that bans private plans from covering abortion and defunds Planned Parenthood — both of which are critical policies for pro-life activists. The parliamentarian has yet to weigh in on the Cruz amendment, which hasn’t been scored by the CBO yet, but there’s a decent chance it fails.

Senate and House leaders might be able to rework their legislation in a way that satisfies the parliamentarian. But if that fails, it could be harder to negotiate a compromise everyone can agree on.

At that point, an option would be to have the presiding officer ignore the parliamentarian’s guidance, which is technically allowed but would be a nuclear procedural change that could enable Democrats to pass sweeping policy changes in the future.

"If you do it once, you’ve blown a hole in the way the Senate works," Binder said.

It’s unlikely enough Senators, some of whom have already expressed their unease with the process so far, would go along with it.