recursive action

[elhetch]

i dont understand how this code works, as per my understanding every time the def function will be called , why it returns a result.

def rabbits(n):
    if n<1:
        return 0
    else:
        if n==0 or n==1:
            return 1
        else:
            return rabbits(n-1)+rabbits(n-2)-rabbits(n-5)