A policy is made up of written documents of a contract for insurance between the insurance company and the insured. Such documents include forms, endorsements, riders and attachments.
A policy number is a unique identifier that attaches a policy to a specific individual. A policy number is assigned to a policy by an insurance company once you have purchased insurance from them. This number is a reference point for the insurance company. The number, varying in length depending upon the insurance company, will be listed on your insurance card.
If you are in an accident you normally would provide your insurance policy number to the other party. With this number the other person can call your insurance provider and place a claim. Also, state agencies, such as the department of motor vehicles (DMV), can verify that you have the required insurance by getting your policy number and checking with your insurance company that your policy is still valid. A policy number typically replaces a binder number, if one is issued.