He campaigned on repealing/replacing Obamacare/ACA. He has thus far been unable to do so because they (GOP) never thought up of a replacement and too many people are reliant on ACA who are also Republican voters to risk pissing them off.
Private insurance, either out of pocket or through your employer.
ACA, which you sign up and pay for but a lot less than private, I think?
Medicaid, which is like ACA but older, administered partially on the state level (every state's Medicaid is a little different and isn't transferrable across states iirc), covers more but has more strings attached (income, overall health, etc).
Medicare, which is the "everything is free" but only available to seniors/disability.
There's also Veteran's Affairs health whatever the hell it is they do, for veterans only.
Emergency rooms are, I think, by law, obligated to treat you, regardless of your ability to pay. Paying for said treatment involves either going into crippling debt or begging on GoFundMe. Some people also simply eschew healthcare entirely because they're afraid of the debt, and sometimes those
people just die.