After a failed attempt, House Republicans Thursday passed a revamped health care bill that would repeal much of the Affordable Care Act (a.k.a. Obamacare) and replace it with a new system.

House GOP leaders pulled their American Health Care Act without a vote in March after facing widespread opposition from moderates, who worried it would leave millions of Americans unable to afford health insurance, and conservatives, who complained it saddled insurers with too many consumer protections.

The revamped bill managed to squeak by with enough votes in the House to pass, though, thanks mainly to a series of major concessions to the conservative House Freedom Caucus and much smaller concessions to wavering moderates. Here’s what’s new in the bill, what remains from the old one, and what the overall package means for your health care.

What’s the latest?

The biggest change concerns pre-existing conditions.

Under an amendment to the bill negotiated by Rep. Tom MacArthur (R-NJ) with the conservative House Freedom Caucus, states can seek a waiver from Obamacare’s current requirement that insurers charge people the same for coverage regardless of whether they have a pre-existing condition.

Related: Personal tragedy drives MacArthur on health care

If states opt out, insurers can charge sick people far more for plans if their coverage has lapsed and coverage also might not include treatments for their condition. States that go this route would have to set up some kind of mechanism, like a high-risk pool, to try and help otherwise uninsurable consumers get coverage.

This is a major shift. In unveiling their first bill, House GOP leaders had explicitly said insurers should not be allowed to charge consumers more and their reversal caused some members who had previously supported the legislation to waver. The moves built on a previous change to placate conservatives that allowed states to opt out of Obamacare's “Essential Health Benefits,” a suite of 10 basic categories of services like hospitalization and prescription drugs that all plans must cover.

The MacArthur amendment brought conservative members and activist groups back on board, but scared off some other Republicans who worried the changes left vulnerable constituents without important protections.

To bring them back, Rep. Fred Upton (R-MI) negotiated another amendment that provides $8 billion over five years to help fund high-risk pools in states that opt out of existing protections on pre-existing conditions. This is in addition to $130 billion in temporary funding over 10 years designed to help states stabilize their insurance markets.

But health policy experts say the money falls far short of what would be needed to provide affordable insurance to people who can’t obtain it otherwise.

“This is a drop in the bucket,” Matthew Fiedler, a fellow at the Brookings Institution's Center for Health Policy, told NBC News.

Related: What Are Pre-Existing Conditions and What Would the GOP Bill Do?

Thomas Miller, a fellow at the American Enterprise Institute, said it was difficult to predict how much funding high-risk pools might need given the uncertainty surrounding the bill. But the politics were easier to suss out.

“It covers one other important constituency: The rear ends of members who have to come on board (to support) the final bill,” Miller said.

Previous attempts at high-risk pools in states often ended up with limited participation as customers faced higher premiums or plans that would not cover costs related to their illness for a designated period.

“Even with all the layers of funding in the bill and the subsequent amendments, the money falls short of what would really be necessary to cover the cost of people with pre-existing conditions,” Larry Levitt, Senior Vice President at the Kaiser Family Foundation, told NBC News.

AARP, the advocacy group that represents seniors, warned that the Upton amendment "would do little to mitigate the massive premium increase for some of the most vulnerable Americans” which they estimated could spike premiums by as much as $25,000 for those who run afoul of the pre-existing conditions clause.

In what could be an ongoing challenge for Republicans, the major health care interest groups largely oppose the current bill on similar grounds: In addition to the AARP, the American Medical Association, which represents doctors, and the American Hospital Association have strongly criticized the legislation.

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Do we know what would happen if these changes became law?

Not really. Members voted on the bill without any analysis of how much it would cost or who it would cover. Even stranger is that they don’t seem to want to know.

In a highly unusual move for a bill that would reorganize one-sixth of the country's economy, the House moved forward without waiting for a score from the Congressional Budget Office, the non-partisan federal agency responsible for modeling the impact of legislation.

While Republicans have sometimes criticized the CBO's accuracy, Congress has long used it as the gold standard in analyzing policy changes and without that analysis lawmakers are choosing to essentially fly blind. There's no other outside study of the bill's impact and they have not held hearings with experts and policy stakeholders to go over its provisions.

Related: Opinion: HHS Secretary Tom Price writes that Obamacare's on the verge of collapse

This is even more striking because the changes are vast since the last CBO score in March, when it examined an earlier version of the bill.

The previous CBO report found the AHCA would lead to 24 million more uninsured after a decade, 14 million people dropping off Medicaid thanks to major cuts, and dramatic spikes in premiums for older and low-income customers.

Those findings are still significant, but they’ve been overtaken by the various amendments that have been added since then. The CBO now has to consider what happens in states that allow insurers to charge people more based on their health and how likely they are to request a waiver.

The CBO also has yet to examine an equally significant revision from March that would allow states to change the 10 “Essential Health Benefits” that insurers are required to provide to all consumers. This could prompt insurers to start selling less comprehensive plans that bring down premiums, but that might not cover services like maternity care or prescription drug benefits.

Some health policy experts are concerned it would effectively price people with serious conditions out of the market. Under this scenario, healthy people would congregate toward skimpy plans that cover few services, while people with expensive conditions would be unable to find affordable plans that cover their treatment.

Determining the implications of the latest changes isn’t easy, but it’s not a sign of confidence in the legislation that neither Congress nor the White House is interested in finding an outside analysis. White House Press Secretary Sean Spicer said on Wednesday it was “almost impossible” to determine the impact of the AHCA, despite the president's boasts that it would improve care across the board.

What if I get my health insurance through my employer?

The bill deals mainly with the individual insurance market, but there are potentially serious changes Congress might not have intentionally considered.

Some health policy experts say that allowing states to waive Essential Health Benefits in the individual market could have spillover effects in the much larger employer market which could cause plans to cover significantly fewer expenses.

The rules on what employer plans have to cover are based on state requirements. Right now it’s not an issue because there’s a minimum federal standard everywhere, but that would likely change under the House bill. If an employer plan uses a deregulated state's definition of Essential Health Benefits, it could open them up to annual or lifetime limits on procedures that the law currently requires employer plans cover but are no longer considered "essential."

These kinds of limits were common in employer plans before the ACA banned them and companies could potentially seek out plans tied to these less-regulated states as a way to cut costs.

"While these protections are very important, most people do not know they have them, and I would expect business groups to push hard to retain the flexibility to choose among state definitions of EHB," Fiedler, the Brookings fellow, told NBC News.

Remind me what the rest of the GOP plan does?

It gets rid of Obamacare’s system of subsidies for people who don’t get insurance through work or government programs and replaces it with a less generous system of fixed tax credits. It cuts Medicaid, which was expanded under Obamacare, by $839 billion over a decade, changes the program's structure, and uses the savings to do away with taxes on wealthier Americans and medical industries that were used to pay for the ACA. It also eliminates the penalty for people who don’t buy insurance, which is commonly known as the individual mandate.

Who benefits? Who doesn’t?

Older patients on the individual insurance market would see big spikes in their premiums, while lower-income families would face higher deductibles and out-of-pocket costs. In a widely cited finding by the CBO, a 64-year old making $26,500 a year would have seen their annual premiums shoot up by $12,900 on average and received less comprehensive insurance under the March version of the bill.

It’s not entirely clear how the newer bill would change that calculus, but there’s not much to indicate the situation for lower-income families or older consumers would be significantly improved and they’d be more vulnerable than other groups to any changes to pre-existing condition protections.

Large numbers of Medicaid patients would lose their coverage: 14 million fewer people would be on the program after a decade, according to CBO. States may have to reduce Medicaid in response in response to cuts as well, which could disproportionately impact seniors and people with disabilities.

On the other hand, younger and healthier patients with higher incomes who buy insurance on the individual market could see their premiums go down and possibly get some federal aid they would not have qualified for under Obamacare. The tax credits top out at incomes of $75,000 for individuals versus about $47,000 for ACA subsidies. Wealthy earners would also get a tax cut. People who don’t want insurance and thought the penalty was unfair would be free to go without coverage.

This split between winners and losers is due to a variety of changes. The bill provides a fixed tax credit instead of Obamacare’s subsidies, which guarantee that consumers who qualify for help don’t have to pay more than a certain percentage of their income on premiums. That means even if premiums go up by a large amount, which happened in many states last year, recipients are largely insulated from the sticker shock. Under the AHCA, though, if your fixed credit isn’t enough to afford insurance, you’re stuck.

A lot of people who can afford coverage now would run into this problem. Premiums vary wildly from region to region, even within the same states, and older customers pay more than younger people. This problem is especially pronounced in rural areas, where health insurance tends to be more expensive. The GOP plan also allows insurers to charge older customers five times more than younger ones, versus three times more under current law. Those who do find insurance would get less help with out-of-pocket costs as well: The bill repeals billions in Obamacare subsidies to help low-income consumers pay for medical expenses and allows insurers to offer plans that cover less than they do now.

It’s not clear how many people would lose insurance entirely. CBO estimated 24 million fewer people would be insured under the March edition of the bill thanks to the combination of Medicaid cuts and changes to subsidies for private insurance. But some of the more recent changes to Essential Health Benefits could reduce that number by allowing states to offer cheaper plans people would more likely be able to afford with their tax credits.

That creates its own scoring challenges, though: Does it count as having “insurance” if you can find a plan that has low premiums, but would leave you on the hook for major medical expenses? It could also raise the cost of the bill: If people can find at least a limited form of insurance, they might be more likely to use the tax credit in the Republican bill to buy a plan rather than leave it untapped.

Is this what Trump said he'd do?

No. Trump ran on repealing Obamacare, but he distanced himself from other Republicans by promising his plan would provide "insurance for everybody," lower deductibles and costs, and would not include Medicaid cuts. This bill is likely to cover far fewer people than Obamacare, allows insurers to raise deductibles and out-of-pocket costs, and cuts Medicaid by large amounts.

Trump has also insisted the bill would match Obamacare’s protections for people with pre-existing conditions — instead it allows states to do away with them, leaving customers potentially on the hook for higher premiums, fewer subsidies, and insurance that may not cover needed services. He’s not alone in this regard: The House GOP boasted on its website debuting the AHCA that “Americans should never be denied coverage or charged more because of a pre-existing condition.” In fact, the latest version of the law explicitly allows people to be charged more because of a pre-existing condition.

What happens now that the bill has passed in the House?

It moves on to the Senate, where there has been considerably less movement on health care. Senators face the same spotlight the House members have for the last two months, including enormous pressure from conservative supporters and the White House to pass something, and from activists and constituents who oppose the bill and want them to scrap it.

The margin for error is slimmer than in the House: Republicans have 52 votes and can only lose two. (Vice President Mike Pence would break a tie). There are conservative and moderate factions with serious concerns, but the moderates may be an even bigger obstacle on the Senate side than they were in the House. It’s unlikely the House bill would pass the Senate in its current form and House members voting for the bill fully expect the Senate to make significant changes.

The wildcard: Many of the big recent changes to the House GOP bill, including its state waivers for Essential Health Benefits and pre-existing condition protections, could run afoul of "reconciliation," the procedure being used to pass the bill in Congress. If the Senate parliamentarian decides the measure violates rules requiring reconciliation items to directly relate to the budget, the deal House leaders made to win over conservatives could be erased.