When you get valid code and enter it, your phone will be unlocked permanently. When you use a SIM card from another carrier, it will usually asks you to enter a SIM network Unlock PIN Code. Majority of mobile devices on the market can be unlocked with a network Unlock Code.
SIM network Unlocking means, you remove this network lock, and use your device with any SIM from any compatible mobile carrier network. Some mobile devices are restricted (locked) to specific carrier network, meaning that your device will only work with their SIMs and will not accept SIM cards from other providers.
