The percentage of the bill you pay. After you have paid your deductible, your insurance company will cover the majority of your health care costs and you are only responsible for a "coinsurance" portion. For example, suppose your plan has 20% coinsurance, you've already paid your deductible, and you need a $10,000 surgery. You would pay a maximum of $2,000 and your insurance would pay the rest.
Stride Tip: If you expect to see a doctor frequently or have a chronic condition, you might want to look for a plan with low coinsurance. These plans generally have higher monthly premiums, but you could end up saving money in the long run by paying less each time you need care.