It's not a silly question at all.
My motto #1: "You've got to start somewhere."
My motto #2: "If you don't know, ask."
Most all of us here love to help beginners because they are trying to learn.
@dbhunia gave you good advice.
From what he responded you can clearly see that AutoCAD can accept AutoLisp coordinate input just as you might enter it from the keyboard... x,y and even x,y,z as a string.
But if you need to mathematically process the point, then you probably want to convert it to the same format that one would be returned from the getpoint function... (x y z) as a list of reals.
Here's what I use:
;; Function to convert a string with delimiters into a list
;; pat is the delimiter and can contain multiple characters
(defun @str2list (str pat / i j n lst)
(cond
((/= (type str)(type pat) 'STR))
((= str pat)'(""))
(T
(setq i 0 n (strlen pat))
(while (setq j (vl-string-search pat str i))
(setq lst (cons (substr str (1+ i)(- j i)) lst)
i (+ j n)
)
)
(reverse (cons (substr str (1+ i)) lst))
)
)
)
For example:
Command: (setq a "5.7,7.8")
"5.7,7.8"
Command: (@str2list a ",")
("5.7" "7.8")
Command: (mapcar 'read (@str2list a ","))
(5.7 7.8)
I hope that helps you.