What does k does in f(n-i,k) and how do we get the value for f(n-i for every step)

We use recursion in f(n-i,k) but how do we get value for f(n-i because we only know if n=0 then we return 1 and we dont have f(0) then return 1.So when recursive call takes place in call staack how do we get values for f()