Unlocked cell phones are cell phones that have been unlocked.. A locked cell phone phone will only recognize the SIM Card (Subscriber Identification Module) of a specifc carrier. Unlocked cell phones will recognize the SIM Card from any carrier. Locking a cell phone is a way for the carrier to require the customer to stay with the carrier for service. Unlocking the cell phone allows the cell phone user to choose any carrier.

Third party carriers may often unlock a cell phone for a fee, however, there is not 100% that all cell phones unlocked by third parties or which have been hacked will operate normally. Many times the cell phones will work correctly but there is not a guarantee.