Difficulties about "Palindrome" (resolved)

I did not understand the part where it has function of "make-palindrome" again.
I was confused about  why would we put another same function in one.
"(define make-palindrome s)
...
(else (string-append
               (substring "Danny" 0 1)
               (make-palindrome (substring "Danny" 1))
               (substring "Danny" 0 1)))"

As I asked one of my friend, he recommended me to set an example and use my note and pen to write all steps out. After doing that, I finnaly got to know that their functions are exercising same way but they mean all diffrent things.

<RESOLVED>