They depend on the environment that people are speaking in. 'come back' refers to the location of the speaker as the point that he/she will return to. example (drinking coffee at a cafe): I really want to come back to this cafe. 'go back' refers to a different location that the speaker is not located at example (drinking coffee at work): He really wants to go back to the cafe

Come (Back) From There to Here. Go (Back) From Here to There. That is the simplest definition of it. Back is mostly optional (Actually just don't omit it if the context isn't clear) and just adds the information that you already have been in the place where the destination is :D Back is necessary in situations like these: "Please come back." would mean "Please move to me where you were before from where you are " "Please come" would mean "Please move to me from there to here" "Could you go back and grab the phone?" would mean "Could you move to the location you were before and grab the phone?" "Could you go and grab the phone?" would mean "Could you move to the location you HAVEN'T BEEN THIS TIME and grab the phone?" Hope I helped

Come back infers that there person is the in that place and should come back where you are. Go Back means that the person when to the place and already came back and need to visit again.