Situation 1. 90% of phones just need the first code (1111111111111111 from example) named the network unlock code or nck. Use this first code when your phone is asking for "Unlock SIM block" or "Enter SIM Network unlock key" .
Situation 2. For some networks like Telus or Metro pc if the first code is not working,use the second or third code named service provider codes or SPK (2222222222222222 or 3333333333333333 from example). This are normally needed if the phone asks when turning with a sim from different carrier to " Enter service provider code "
Situation 3. In case you inserted too many wrong unlock code and your phone asks for "Simlock Block Unlock Reset Key" or something similar,use the last code (4444444444444444 from example),and that will reset the unlock counter and phone will start asking for network unlock code and will have to insert the first code or second code like shown in situation 1 and 2.