Hai, Switch on your mobile phone with a sim card from a network other than the network you are currently with. If you are able to use the phone, you can be sure that your phone is not locked. If your phone displays an error message saying "Wrong sim" or "Incorrect sim" or "Emergency calls only", etc., then your phone is probably locked. Otherwise your phone is unlocked.
Unlocking is the process of releasing your network lock. So only you can able to use all gsm network in your mobile. Remote unlocking method is easy way to remove your network lock. If you want to unlock your iPhone you can visit this site Simpleunlocking.com . They will help you to unlock your iPhone remotely. After unlock you can use all gsm sim cards.