Insurance companies' guidelines and auto insurance policy terms differ so while in general when you give someone permission to drive your vehicle your insurance coverages extend to them, there are some exclusions.
Some policies may have exclusions for drivers under a certain age (under age 21 or under 25 are normal exclusions), for drivers with medical conditions and and exclusion that allows an insurer not to cover a vehicle if the driver is not licensed or driving without a valid license.
So before loaning your car to anyone, especially an unlicensed driver, you will need to read through your insurance policy and speak to your agent to make sure your full insurance coverages will cover those that you let use your vehicle. If your coverages will extend to others that you let borrow your car then you would can find out from your insurer's claim department how to place a claim if that person was to be in an accident.
If your coverages will not extend to a person driving without a license then you should remember that as the car owner if that person is in an accident then you, as well as the driver, can usually be held liable for whatever damages the driver may cause others. Also in some states if you allow someone to drive a car that does not have a valid license the you may be cited for permitting this unlicensed person to operate your vehicle illegally.