President Trump told Fox News last week that when it comes to ObamaCare, “we’re going to have a plan that’s going to be great for people.”

What that plan will actually be, though, remains unclear.

Trump has said that he will put forward an ObamaCare replacement plan shortly after Rep. Tom Price (R-Ga.) is confirmed as secretary of Health and Human Services, an announcement that caught lawmakers off guard.

If Trump actually follows through on putting forward his own plan, rather than letting Congress take the lead, it could provide some guidance to Republican efforts to come up with an ObamaCare replacement, though lawmakers are sure to want their own say on any plan as well.

Trump has dropped a few hints on his ideas for a replacement plan.Here’s a guide to what we know and don’t know.

He wants to cover everyone.

What we know: Trump made waves last week when he told The Washington Post he wants everyone to have insurance.

“We’re going to have insurance for everybody,” Trump said. “There was a philosophy in some circles that if you can’t pay for it, you don’t get it. That’s not going to happen with us.”

This remark sounded more like Democrats’ goal of universal coverage than Republicans’ usual focus on reducing costs and regulation in healthcare.

Republicans on Capitol Hill have been pivoting back to the idea of everyone having “access” to coverage. It is not entirely clear what the difference between universal “access” to coverage and universal coverage is. For one, Republicans don’t want to have a mandate for people to get coverage, so some people could choose not to buy it.

But Democrats fear that the emphasis on “access” over actually having coverage is code for not really providing enough financial help for people to have affordable insurance.

“I have access to buying a $10 million home,” Sen. Bernie Sanders (I-Vt.) said at Price’s confirmation hearing. “I don’t have the money to do that.”

What we don’t know: Trump has provided almost no details of how we would actually go about providing insurance for everyone, a lofty promise that would be extremely hard to fulfill, especially after repealing ObamaCare and rolling back its coverage gains for 20 million people.

Trump did put forward a healthcare plan on his website during the campaign, but it consisted of standard Republican ideas like allowing insurance to be sold across state lines and creating a tax deduction for health insurance. The Committee for a Responsible Federal Budget estimated the plan would result in 21 million people losing coverage, largely due to the repeal of ObamaCare.

He wants block grants for Medicaid. 

What we know: One detail of health policy that Trump has repeatedly stressed is block grants for Medicaid. That means that the federal government would give states a set amount of money for the low-income health insurance program, rather than the current federal commitment that is more open-ended.

The expansion of Medicaid was a key part of ObamaCare’s coverage expansion, but that growth could now be repealed.

Republicans say block grants would limit federal spending and give more power to the states. But Democrats warn that limiting the spending would simply mean damaging cuts to the program, keeping people out of coverage or slashing benefits.

Block grants were one of the few healthcare specifics in Trump’s recent interview with Axios.

“Whether it’s Medicaid block grants or whatever it may be, we have to make sure that people are taken care of and it’s going to be a very important part to me,” Trump said.

What we don’t know: It’s unclear how a replacement plan would treat ObamaCare’s expansion of Medicaid. Several Republican governors in states that have accepted the expansion are pushing to keep it.

Another key point that is unclear is how much money would be in a block grant, a crucial fact for how deep any cuts would have to be.

“The difference between a good block grant and a dangerous block grant is in the detail,” Ohio Gov. John Kasich (R) wrote in a letter to Congress.

He wants to keep protections for people with pre-existing conditions

What we know: Trump told The Wall Street Journal shortly after the election that he wants to keep protections for people with pre-existing conditions. ObamaCare prevented insurance companies from rejecting people or charging them more because of their health conditions.

What we don’t know: The question is how a Republican plan could protect people with pre-existing conditions without ObamaCare’s mandate for people to have insurance. The mandate is intended to make sure healthy people sign up, since if enrollees only consist of the sick, premiums will spike.

Republican plans have tried to solve this problem with a less broad protection for people with pre-existing conditions. Republican plans, including Speaker Paul Ryan’s (R-Wis.) outline, call for protecting people with pre-existing conditions only when they are switching plans, in contrast to ObamaCare, which also protects uninsured people signing up for the first time.

Congress has its own ideas.

What we know: Meanwhile, Ryan is pitching the ideas outlined in his Better Way plan.

Ryan told TV host Charlie Rose last week that he wants tax credits to help people afford coverage. For people with pre-existing conditions, Ryan pointed to high-risk pools, which separate out sick people to get government-subsidized coverage.

“We think the smarter way to help people with a preexisting condition is just directly subsidize their care through risk pools,” Ryan said. “And by doing it that way, the rest of the pools of Americans don’t have to cover those losses.”

What we don’t know: Ryan has not provided details like how big the tax credits would be, a crucial point for knowing how affordable insurance would become for people.

Democrats also argue that high-risk pools failed in the past, largely because there was not enough government funding to pay for sick people’s coverage. It is unclear if Republicans would provide enough funding.

Perhaps the biggest unknown: What Trump thinks of the details of Ryan’s plan. He has not commented much on them.

This article originally appeared in The Hill.