Apple Watch GSP only

hello,

i would like clarification on the Apple I watch. For the one with the GPS only can you basically do everything on the the watch, call, text, responding to texts, listening to music without being connected to your cellular plan? Is the only difference between the GPS only and the GPS plus cellular is that the GPS cellular is just like a phone but the GPS only you have to be connected to Wi-Fi in order to do everything? I have tried to do research on this and I can’t get a straight answer on the major differences between the two. I have a fit bit and I like that I can see who is calling me or I can see who is texting me and what their texting me. It would be cool to be able to respond to a text message through the Apple Watch but do you have to have the GPS plus cellular in order to do that? Any information you can give me regarding the two different types of watches would be great.