Memory addressing question

Forgive me if this sounds like a newbie question. Any time you obtain a stack address from a pointer, what is this relative to by default? Is it the extra segment, the stack segment, what? How do you change change the relative positioning in memory? Thanks in advance

In what context are you talking? C or some other high-level language, or assembler? If it's the former, addresses aren't relative to anything - they should be taken as absolute (though in reality they're virtual addresses, not absolute physical addresses). Applications at this level don't have to deal with segments at all.