What does this scheme function do?

Question

Before someone asks, this is not a homework, I am a Spanish major, but I would like to understand some programming...

(define (x lis)
  (cond
    ((null?? lis) 0)
    ((not (list? (car lis)))
     (cond
       ((eq? (car lis) nil)
        (x (cdr lis)))
       (else (+1 (x (cdr lis))))))
    (else (+ (x (car lis))
             (x (cdr lis))))))

Answer 1

you got a party to go to tomorrow night and got no time for your CSC 519 assignment ??

Answer 2

counts non-nil leaves of a tree