Kind of. Insurance companies make deals with healthcare providers to give better rates on procedures than the book price. The book price is the price that the care provider "officially" charges. Usually it is some bullshit number they pull straight out of their ass. If you do not have insurance, they will charge you that made up book price. But you can call them up and negotiate with them because they want some payment and they realize most people cannot pull $50k out of their rectum.
So back to insurance...they negotiate with certain care providers in the region they operate. Those are in network and get better rates. Ones outside of that network get worse rates and insurance generally does not cover most of the cost...unless you have hit your out of pocket maximum for the year. The out of pocket maximum is when you have spent so much out of pocket on things like co-pays and out of network costs that insurance will now start covering 100% of the medical bills.
Not confusing or fucked up at all, right? It gets more complicated because there are also deductibles. That one is similar to out of pocket maximum but insurance does not pay 100%, generally closer to 80%. Your deductible goes toward the out of pocket maximum.
Before Obama, insurance companies also had maximum lifetime benefits. Basically if you were costing them too much for shit like a heart transplant, they'd tell you to fuck off after they already paid out $500k or whatever number they chose.
They could also deny coverage for a pre-existing condition. Generally you would be fine for that one if you had continual coverage but not necessarily. So if that heart transplant person wanted to switch insurance because he had a new job, they could see that he had a transplant previously and decide to not cover them. That one is a bit personal to me because my wife and her mother had a similar issue. My wife had a liver transplant when she was young. My mother-in-law did not ever try to switch jobs because she was afraid that a new insurance would not cover my wife. Dialing in the proper dosage for a growing kid so their liver does not get rejected takes a lot of doctor visits and would have been very costly.