Hired and Non-Owned Auto is third party liability coverage for your drivers who make deliveries using their own vehicle.
Hired Auto is the use of a vehicle rented for company use in the company name. The coverage acts in excess of your driver's own insurance. Your coverage can be triggered when the driver's insurance maxes out its limit but damages are above their limit.
Your coverage can also be triggered if the drivers insurance is for whatever reason unavailable. HNOA does NOT cover your driver's vehicle under any circumstance.