Part of health insurance is a bit like fire insurance on your house. There is a really small chance that your house will burn down next year (say 1 in 10,000) but if it does you'll lose a ton of money (say $500,000). So you pay $55 to get a year of fire insurance (500,000 / 10,000 = 50 + 5 in profit for the insurance company).

This is a great deal for you. $55 is no big deal and now if your house burns down you don't suffer a tremendous financial loss.

Similarly there is a really low chance you'll get cancer next year. But if you do it could cost a ton (millions of dollars possibly) to treat. So insurance is a good deal for this too.

Now, in the US 2 other things get lopped on to health insurance that make things a bit more complicated:

1) For a lot of people health insurance covers cheap and predictable expenses like an annual checkup. There are a lot of people that think using insurance for this is a bad idea. But some people think it's a good idea. It's complicated.

2) Health insurance (especially after Obamacare) can be a form of social insurance where healthy and/or rich people pay more than they otherwise would so that unhealthy and/or poor people pay less. This reduces economic inequality. There is a lot of political disagreement about whether this is a good idea.

Did this help? I've glossed over a ton of details but maybe it's enough to get started.