It means almost nothing... unless you get sick or run over by a car. My family skated by for years without health insurance. We even had two babies while uninsured. We lucked out and came out ahead. We saved far more by not paying insurance premiums than we paid on checkups, vaccinations and even the delivery of two babies. If my wife had to have a c-section or there were other complications things would have been quite different.
Edit: Also, if you just lost your insurance and you want continued coverage, look into COBRA coverage.
Wow, so it is really possible to not have an insurance coverage until you get old. I know without insurance is financially risky but then seeing this post makes me think that I can still live without insurance. The cost of insurance is really something these days so I think if you're not an accident prone magnet, you can still live without having to pay for insurance.
Sorry, that's not the point I wanted to get across. It's really going to be random. Even if you are the pinnacle of health, you can still be involved in an accident of some sort which can ruin you financially. There are a ton of things which could have gone wrong for us and put us in a very bad situation, but we got lucky. A friend of mine has three kids and all three of them had to be delivered via c-section. That alone could have added up to well over a hundred thousand dollars in medical bills. Fortunately he had some coverage but was still on the hook for close to $10k due to coinsurance.