"tail recursion" SICP problem

Hello.

I read SICP and I find it hard to understand the "tail recursion". He says the book, which is a function of "tail recursion"as he calls himself, and not the other functions. But she does not "tail recursion":

(define (f n)
           (if (= n 0)
             1
             (* n (f (- n 1)))))

This is the "else branch"is called. What's up?

(To my English, forgive me am German makes happily speaks, because I, and to the English.)

>>5
I do not see the difference. Both functions are called f that "else branch." Please help.