In the states with no-fault insurance, insured drivers are typically paid for medical expenses by their own insurers, regardless of who caused the accident. Nonetheless, BI liability coverage is still required in no-fault states because if injuries are bad, the at-fault driver may be sued by the injured party. If that happens, your BI coverage can help cover your liability expenses.
Collision coverage has a deductible, which is the amount you pay before your coverage helps pay for your claim. You can typically choose the amount of your deductible when you buy coverage. So, if you choose a $1,000 deductible and your car is later damaged in a covered accident, you'd have to pay $1,000 toward repair costs. Your collision coverage would help pay the rest, up to your coverage limit.