The unlocked iPhone includes all the features of iPhone but without a wireless contract commitment. You can activate and use iPhone on the supported GSM wireless network of your choice. The unlocked iPhone 4, iPhone 4S and iPhone 5 will not work with CDMA-based carriers. An unlocked iPhone 5 may not support LTE networks in all other countries; contact service providers for details.
If you don’t want a multiyear service contract, or if you prefer to use a local carrier when travelling abroad, the unlocked iPhone is the best choice. It does not come with a micro-SIM card for iPhone 4 and iPhone 4S, or a nano-SIM card for iPhone 5, so you’ll need to get one from any supported GSM carrier worldwide. To start using it, simply insert the card into the slot on your iPhone and turn it on by pressing and holding the On/Off button for a few seconds. Then follow the on-screen instructions to set up your iPhone.