Is it fair to say to someone just starting out a TYPICAL sketch is divided into three sections?
Global, Setup and Loop?
Not really - if you think about it, both setup and loop are globals too.
I've been reading an it appears most commands can be used in setup as well as in loop
Both setup and loop are functions. There is nothing special in the language about either of them.
Anything - literally - you can put in loop, you can put in setup. It may not behave as you expect or wish, but that is nothing to do with the language, more to do with the structure of main/setup/loop.
int someVariable; // A global variable
void setup (void)// A global function
{
}
int anotherVariable; // also a global variable, BUT!
void loop (void) // Also a global function
{
}
Can you figure out what the big BUT is?