Co-Insurance: After paying the deductible, percentage or amount of covered expenses that the insured pays. For example, an insurance policy brochure may mention that the policy will pay 80% of the first $5,000 and 100% thereafter of the usual and customary charges; In some health insurance plans, it is also called "co-payment".
Deductible: Amount to be paid by the insured person before the insurance company begins to pay for the covered expenses. Deductible may be either per sickness/injury or once per policy period or once per year depending upon the insurance policy you purchase. You will not get receive any reimbursement later from insurance company for the deductible you pay. e.g., Let us consider that you have purchased an insurance policy with a $50,000 policy maximum, $250 deductible per policy period and 80/20 co-insurance. Suppose you incur a covered expense of $10,250; then the insurance company will pay the covered expenses according to policy terms after you make a a payment of the deductible (i.e. $250).