Adder Closure example/question

adder.lisp

(defun make-adder (x)
  (lambda (y) (+ x y)))

(defun add-5 (x)
  (funcall (make-adder 5) x))

(defun add-6 (x)
  (funcall (make-adder 6) x))

(add-5 20)
(add-6 26)