Jailbroken is jailbroken...
It basically allows you to do things apple doesn't want you doing, like putting non approved apps on (be it cracked, or just non approved) a good example is the iPhone 2g, and 3G, never had video cameras on them, a jailbroken phone will let you download an app to use the still camera to record videos...
My iPhone 4, is locked to Rogers, but because it's jailbroken, I can download a package (similar to an app) that unlocks it, and let's it be used on any carrier, I can also use FaceTime over 3G, (it requires wifi normally) I can download apps that are larger than 20mb, over 3G, and a multitude of other things, like creating a wifi hotspot with my phone (stock you can only do USB or Bluetooth)
It basically allows you to do things apple doesn't want you doing, like putting non approved apps on (be it cracked, or just non approved) a good example is the iPhone 2g, and 3G, never had video cameras on them, a jailbroken phone will let you download an app to use the still camera to record videos...
My iPhone 4, is locked to Rogers, but because it's jailbroken, I can download a package (similar to an app) that unlocks it, and let's it be used on any carrier, I can also use FaceTime over 3G, (it requires wifi normally) I can download apps that are larger than 20mb, over 3G, and a multitude of other things, like creating a wifi hotspot with my phone (stock you can only do USB or Bluetooth)