can you tell me what the different between factory unlocked and open line phone

I have no idea what an "opne line" cell phone is.

A "factory unlocked" device is one sold directly by Apple or an officiall Apple authorized reseller without any SIM card lock in place restriciting it to one Cell Service Providers SIM cards and network. Such an unlocked iPhone will accept any SIM card from any compatible GSM service provider. And such a phone can be switched form one carrier to another at will.

Note that there is no such thing as an unlocked CDMA device - all CDMA iPhones have the CDMA side permaently locked to the carrier they are sold with service for (CDMA locking is technically quite different from GSM SIM slot locking, and CDMA locking effectively cannot be undone).

There are resellers who sell iPhones at full retail price (i.e. no carrier subsidy) and without a service contract, but they are still locked to a specific carrier (or they will lock to the carrier the first time a SIM is inserted and service is set up). So a no-contract iPhone is not necessarily an unlocked iPhone.

Neither term makes any sense. Apple never says "factory unlocked" as there is no such thing. Most people who use that term mean that the phone was hacked in the "factory" behind their store, or in their garage. A phone's lock status is set when the phone is first activated, based on a master database of all iPhone serial numbers maintained by Apple, but populated by carriers.

I've never heard the term "open line".

If you want a legitmately unlocked iPhone there is only one way to get one new: Purchase it directly from Apple, pay full price, and be sure to specify "unlocked". Some carriers will also unlock a phone, either for a fee, or if the original owner's contract has been satisfied for no charge.

If you are in the UK Carphone Warehouse sells phones that it says are "SIM-Free". DO NOT BUY ONE OF THESE. SIM-free means the phone can be used with any carrier, but the first time they are activated they become locked forever to the carrier they were activated with.

There is no such thing in Apple's vocabulary as" factory unlocked"

All iPhones come out of the factory the same "open line" (with certain exceptions in US )

Carriers when they sell in most cases apply a lock to ensure only their services are used and since they usually subsidise the cost of the handset this is probably reasonable

Many carriers will offer to unlock their iPhones once the user meets the requirements laid down by each carrier

Apple sell "open line" iPhones from their stores and online store

Most other iPhones will be locked to a carrier

a google for what open line phone is never heard the term before tell thats it just mean a sim unlocked phone

in which case the only difference would be that a factory unlocked was never sim locked and a open line phone could have been unlocked by the carrier after the binding was over