Is a insured driver covered while driving someone Insured car?

Yes, in most cases if you have permission form owner, you're coverage from your policy extends when using someone else. There may exceptions with a commercial vehicle used with an exclusion or with no coverage or the policy may also state you're only covered in another vehicle for liability only .

You should clarify this with your carrier directly or check with your agent regarding what your policy states specifically on driving another car to ensure if your fully covered .