Hi a unlocked iphone is nothing but your iphone can be freely used with any GSM sim ...If the iphone is locked to any particular network provider then you can't use any other GSM sim in it until you unlock it ...You can easily unlock your iphone using sites like WickedUnlock.com here they are rendering remote unlocking service to unlock all model iphone from network lock .You first check that whether the service is available for your country and network provider .If yes then pay for it and unlock your iphone then freely use it with any GSM sim ..