Why is it important to no the difference between co-insurance and deductible?

A deductible is the initial amount that the insured must pay out of pocket before the insurer's obligation to pay anything is triggered. It might be best understood as the amount for which you have agreed to self-insure before seeking assistance from the insurer. For example, if you have a $1000 collision deductible on your auto insurance, and a collision results in repair costs of $650, you would not have met your deductible, and the collision insurer would not have an obligation to pay.

In contrast, co-insurance is that percentage of a covered claim that you are obliged to pay. The context of health insurance probably provides the best example. A major medical policy may provide for a 20% copayment. This means that once any deductible is met, the insurer pays 80% of allowable charges, and the insured is responsible for the remaining 20%.