When a new policy is taken out, the insurance company will want to list every person living in your household, even those who do not drive. These listed names are then placed into several categories, including excluded, included, and not rated. Which category a person fits into will determine what effect, if any, that person will have on your premiums.
For instance, if you have a 20 year old living in your home who does not drive or have a driver license, that person may be listed as not rated on your policy. This means that the person is not specifically excluded from the policy, but listing them will not have an effect on your insurance premiums.
In another scenario, a person can be both not-rated and excluded from the policy. This means that the person does not affect your insurance rates, but if that person is involved in an accident, the insurance company will deny any claims you file. Excluded people, whether they are rated or not, only affect your insurance premium if that person is driving and involved in an accident. Because they were excluded from operating the vehicle, you will be responsible for any injuries or damages, and the insurance company may raise your rates or cancel the policy because an unapproved person was driving when the accident happened.
People can be not rated because they are not licensed drivers, because that person has their own vehicle and insurance, or several other reasons. not being rated simply means that the person will not affect your insurance rates, and any additional comments, such as included or excluded, determine whether the person is entitled to file a claim.