Is there a Difference between the SIM code and the SIM unlock code?

Yes! There is a big difference!

Sim Network unlock Pin is quickly misinterpreted as the 4 digit PIN number connected with your SIM card, nevertheless this is not the case.  The Sim Network unlock Pin is in fact the unlock code to open your Network. This is frequently called, the Network Unlock Code, Network Control Secret (NCK), Master Unlock as well as other terms.