JAIL BREAK vs UNLOCK 
  
Jailbreaking allows you to install 3rd party applications, customize graphics, sounds, etc. 

Unlocking allows you to use the phone on networks other than AT&T. 


or


jailbreaking is basically the unlocking of the firmware to force the phone to allow 3rd party applications.

Unlocking, however is a process for now impossible to achieve on the iphone without jailbreaking as it requires a third party app to be loaded to the phone.

Jailbreak + not AT&T sim = inoperational

Jailbreak + anySIM + non AT&T sim = perfectly working phone.