What's the difference between factory unlocked iphone and normal unlocked iPhone?

Anyone know? Is there even a difference?

Factory unlocked iPhones are iPhones that never been locked to any network. They came out of the factory as an unlocked phone and were sold as unlocked iPhones.

Unlocked iPhones without the word 'Factory' means that some guy just bought an iPhone off some network provider (like AT&T), then he dropped the contract, then he unlocked the iPhone.

Factory Unlocked iPhones costs more when you buy a brand new one like the $699 iPhone 4S (please double check the price). Locked iPhones to be unlocked later on costs way, way cheaper when you buy it with a contract through a network provider (like AT&T). Some cost like $199.99 but you also have to buy a contract.

To unlocked an iPhone from a network provider can be very very painstaking. Sometimes you have to wait for months, even years for an unlock method to be released. And you have to wait even more when you update your iPhone. Factory unlocked ones are unlocked even if you update them so you might be paying more but you're paying for flexibility and comfort.

Factory unlocked ones are permanently unlocked whereas software unlocked ones only work until the phone is upgraded or restored.

If you update your iphone, normal unlock will be removed while factory unlock will still be there.