Fibonacci - Recursion

Question

I understand how the fibonacci sequence works, but when implementing a fibonacci function - I don't understand what's the given number to the function and what it returns.

def fib(n):
if n == 0:
return 0
if n == 1:
return 1
return fib(n - 1) + fib(n - 2)

Answer 1

Try working out this on pen and paper and visualuze it by tree diagram. ( try on few easy inputs like 1,2,3,4,5 )

You will soon start to see :
f(n)=f(n-1)+f(n-2) for n>=2 and [ f(0)=0 , f(1)=1 ]

That will be much benificial to you!
feel free to ask if you aren't able to

Answer 2

Recommend you to learn how recursion works.