If I create a global variable in a local script is that a variable that only the current client can see or is it shared across all clients?
In other words, I know it is not on the server, my question is, is it global just for the current client, or all clients?
Stuff made in clients, will be only visible for current clients.
So obviously, will not be visible for all clients.
Variables are only visible to the script that initializes them, whether global or not, with the exception of variables created in module scripts. The term global just means that no matter where it is defined it can be called by the script. The term local means that the variable can be called with respect to scope.
The direct answer to your question is that global variables can not be used across different scripts.
If you want actual “global” variables that can be accessed across scripts, then look into _G. Honestly though, I’d recommend module scripts.