According to the Auto Insurance Buyer's Guide on the Ohio Department of Insurance website, typically covered on an insurance policy is you, family members who live with you (that you have listed on your policy) and in general any licensed driver that you allow to drive your car unless your policy rules out this provision.

Your friend will have to discuss the coverage he has under his policy but normally it is the owner's insurance that would be primary and the driver's car insurance would be secondary, thus his insurance would pay on the damages first. If his insurance did not cover all of the damages then your insurance could be used for excess.