what is a locked phone?
Locked / Unlocked. A 'locked' mobile phone is one that has been restricted by software so that it can only be used with a single network or carrier. Locked mobile phones are usually GSM phones that use a SIM card - hence the use of the term 'SIM lock'. The reason for the lock is because mobile phones are usually heavily subsidised and carriers want to discourage people switching networks or shipping phones to other countries.