Auto insurance protects you against financial loss if you have an accident. It is a contract between you and the insurance company. You agree to pay the premium and the insurance company agrees to pay your losses as defined in your policy.
An auto insurance policy is comprised of six different kinds of coverage. Most states require you to buy some, but not all, of these coverages. If you're financing a car, your lender may also have requirements.
Most auto policies are for six months or a year. Your insurance company should notify you by mail when it's time to renew the policy and to pay your premium.