How to make an anonymous function call itself

self-calling-lambda.scm

;we define a function 'starter' which calls its first parameter on itself and the second parameter
(define starter
    (lambda (f arg)
        ((f f arg))))

;we call the 'starter' on anonymous (lambda) function (calling its first parameter on itself and the second parameter) and a number
(starter (lambda (g num)
             (printf "~a\n" num)
             (g g (+ num 1)))
          0)

;the lambda will call itself and will run forewer (with tail call optimalization), printing ascending numbers



;...and calling it all together at the point of definition
((lambda (f arg)
    ((f f arg)))
        (lambda (g num)
            (printf "~a\n" num)
            (g g (+ num 1)))
         0)

Can u explain it plz