What is the difference in between a factory opened and GSM ...

Your question is a bit complicated. I’ll try to address it you can have an unlocked phone from the factory it can be GSM or CDMA. And all that indicates is it will deal with various providers that have those kinds of networks. It does not matter whether the phone is an iPhone or Android device. So for example CDMA phones will work generally in the United States on Verizon and Sprint Networks. GSM phones will work on AT&T T-Mobil networks. Now a phone that is locked will just deal with the particular Network that was intentionally tied to that phone. Once again it does not matter whether it’s an Android phone or an iPhone. So example a locked phone offered by AT&T will just deal with AT&T network here in the United States. A lock phone sold on Verizon’s network will just work on Verizon’s Network here in the United States. For overall versatility these days you constantly wish to buy an unlocked phone that is either CDMA capable or GSM capable, or both. Typical example of a phone that will work on both CDMA/ GSM networks is the Moto G 5 plus.
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