There are lots of phones like that. For example the Samsung Galaxy S4 had different versions as well, weather it was a Verizon locked phone or other carrier or from a different country.
What the “locked” means is that the phone is locked to that carrier. This means you have to use that carrier that phone is locked to in order to service it. If the phone is Verizon locked, you can only service it with Verizon.
If the phone is “unlocked” this means that you can use any carrier. It is not locked to any specific one carrier and you can service it with Verizon, Sprint, AT&T, etc.
Hope this helps.